chore: avoid depending on rbac in slim builds (#17959)

I noticed the `coder-vpn.dylib` (of course alongside the Agent/CLI binaries) had grown substantially (from 29MB to 37MB for the dylib), and discovered that importing RBAC in slim builds was the issue

This PR removes the dependency on RBAC in slim builds, and adds a compile-time check to ensure it can't be imported in the future:

```
$ make build
# github.com/coder/coder/v2/coderd/rbac
coderd/rbac/no_slim.go:8:2: initialization cycle: _DO_NOT_IMPORT_THIS_PACKAGE_IN_SLIM_BUILDS refers to itself
make: *** [Makefile:224: build/coder-slim_2.22.1-devel+7e46d24b4_linux_amd64] Error 1
```

Before and after for `coder-slim_darwin_arm64`:
```
$ gsa before after
┌───────────────────────────────────────────────────────────────────────────────────┐
│ Diff between before and after                                                     │
├─────────┬─────────────────────────────────────────┬──────────┬──────────┬─────────┤
│ PERCENT │ NAME                                    │ OLD SIZE │ NEW SIZE │ DIFF    │
├─────────┼─────────────────────────────────────────┼──────────┼──────────┼─────────┤
│ -100%   │ github.com/gorilla/mux                  │          │          │ +0 B    │
│ -100%   │ github.com/ammario/tlru                 │          │          │ +0 B    │
│ -100%   │ github.com/armon/go-radix               │          │          │ +0 B    │
│ -0.00%  │ gvisor.dev/gvisor                       │ 2.4 MB   │ 2.4 MB   │ -4 B    │
│ -0.21%  │ os                                      │ 155 kB   │ 155 kB   │ -328 B  │
│ -0.23%  │ regexp                                  │ 152 kB   │ 152 kB   │ -346 B  │
│ -0.04%  │ runtime                                 │ 876 kB   │ 876 kB   │ -372 B  │
│ -100%   │ github.com/rcrowley/go-metrics          │ 675 B    │          │ -675 B  │
│ -23.79% │ github.com/cespare/xxhash/v2            │ 3.0 kB   │ 2.3 kB   │ -715 B  │
│ -100%   │ github.com/agnivade/levenshtein         │ 1.4 kB   │          │ -1.4 kB │
│ -100%   │ github.com/go-ini/ini                   │ 1.5 kB   │          │ -1.5 kB │
│ -100%   │ github.com/xeipuuv/gojsonreference      │ 2.4 kB   │          │ -2.4 kB │
│ -100%   │ github.com/xeipuuv/gojsonpointer        │ 5.2 kB   │          │ -5.2 kB │
│ -2.43%  │ go.opentelemetry.io/otel                │ 316 kB   │ 309 kB   │ -7.7 kB │
│ -2.40%  │ slices                                  │ 381 kB   │ 372 kB   │ -9.2 kB │
│ -0.68%  │ crypto                                  │ 1.4 MB   │ 1.4 MB   │ -9.5 kB │
│ -100%   │ github.com/tchap/go-patricia/v2         │ 23 kB    │          │ -23 kB  │
│ -100%   │ github.com/yashtewari/glob-intersection │ 28 kB    │          │ -28 kB  │
│ -4.35%  │ <autogenerated>                         │ 754 kB   │ 721 kB   │ -33 kB  │
│ -100%   │ github.com/sirupsen/logrus              │ 72 kB    │          │ -72 kB  │
│ -2.56%  │ github.com/coder/coder/v2               │ 3.3 MB   │ 3.2 MB   │ -84 kB  │
│ -100%   │ github.com/gobwas/glob                  │ 107 kB   │          │ -107 kB │
│ -100%   │ sigs.k8s.io/yaml                        │ 244 kB   │          │ -244 kB │
│ -100%   │ github.com/open-policy-agent/opa        │ 2.2 MB   │          │ -2.2 MB │
├─────────┼─────────────────────────────────────────┼──────────┼──────────┼─────────┤
│ -7.79%  │ __go_buildinfo __DATA                   │ 18 kB    │ 17 kB    │ -1.4 kB │
│ -6.81%  │ __itablink __DATA_CONST                 │ 23 kB    │ 22 kB    │ -1.6 kB │
│ -6.61%  │ __typelink __DATA_CONST                 │ 71 kB    │ 66 kB    │ -4.7 kB │
│ -2.86%  │ __noptrdata __DATA                      │ 1.0 MB   │ 993 kB   │ -29 kB  │
│ -21.49% │ __data __DATA                           │ 320 kB   │ 251 kB   │ -69 kB  │
│ -6.19%  │ __rodata __DATA_CONST                   │ 6.0 MB   │ 5.6 MB   │ -372 kB │
│ -47.19% │ __rodata __TEXT                         │ 7.6 MB   │ 4.0 MB   │ -3.6 MB │
├─────────┼─────────────────────────────────────────┼──────────┼──────────┼─────────┤
│ -14.02% │ before                                  │ 50 MB    │ 43 MB    │ -7.0 MB │
│         │ after                                   │          │          │         │
└─────────┴─────────────────────────────────────────┴──────────┴──────────┴─────────┘
```

coderd/rbac/no_slim.go

@@ -0,0 +1,9 @@
+//go:build slim
+
+package rbac
+
+const (
+	// This line fails to compile, preventing this package from being imported
+	// in slim builds.
+	_DO_NOT_IMPORT_THIS_PACKAGE_IN_SLIM_BUILDS = _DO_NOT_IMPORT_THIS_PACKAGE_IN_SLIM_BUILDS
+)

coderd/rbac/roles.go

@@ -798,12 +798,12 @@ func OrganizationRoles(organizationID uuid.UUID) []Role {
 	return roles
 }
 
-// SiteRoles lists all roles that can be applied to a user.
+// SiteBuiltInRoles lists all roles that can be applied to a user.
 // This is the list of available roles, and not specific to a user
 //
 // This should be a list in a database, but until then we build
 // the list from the builtins.
-func SiteRoles() []Role {
+func SiteBuiltInRoles() []Role {
 	var roles []Role
 	for _, roleF := range builtInRoles {
 		// Must provide some non-nil uuid to filter out org roles.

coderd/rbac/roles_test.go

@@ -34,7 +34,7 @@ func (a authSubject) Subjects() []authSubject { return []authSubject{a} }
 // rules. If this is incorrect, that is a mistake.
 func TestBuiltInRoles(t *testing.T) {
 	t.Parallel()
-	for _, r := range rbac.SiteRoles() {
+	for _, r := range rbac.SiteBuiltInRoles() {
 		r := r
 		t.Run(r.Identifier.String(), func(t *testing.T) {
 			t.Parallel()
@@ -997,7 +997,7 @@ func TestIsOrgRole(t *testing.T) {
 func TestListRoles(t *testing.T) {
 	t.Parallel()
 
-	siteRoles := rbac.SiteRoles()
+	siteRoles := rbac.SiteBuiltInRoles()
 	siteRoleNames := make([]string, 0, len(siteRoles))
 	for _, role := range siteRoles {
 		siteRoleNames = append(siteRoleNames, role.Identifier.Name)