chore: add agent-connection-watch for workspaces (#24507)

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relates to GRU-18  
  
Adds basic implementation for Workspace Agent Connection Watch and tests.  
  
Missing are handling of logs.

coderd/coderdtest/subjects.go

@@ -0,0 +1,31 @@
+package coderdtest
+
+import (
+	"github.com/google/uuid"
+
+	"github.com/coder/coder/v2/coderd/rbac"
+	"github.com/coder/coder/v2/coderd/rbac/rolestore"
+)
+
+func MemberSubject(userID, orgID uuid.UUID) rbac.Subject {
+	memberRole, err := rbac.RoleByName(rbac.RoleMember())
+	if err != nil {
+		panic(err)
+	}
+	orgMember, err := rolestore.TestingGetSystemRole(
+		rbac.RoleOrgMember(),
+		orgID,
+		rbac.OrgSettings{ShareableWorkspaceOwners: rbac.ShareableWorkspaceOwnersNone},
+	)
+	if err != nil {
+		panic(err)
+	}
+	return rbac.Subject{
+		FriendlyName: "coderdtest-member",
+		Email:        "member@coderd.test",
+		Type:         rbac.SubjectTypeUser,
+		ID:           userID.String(),
+		Roles:        rbac.Roles{memberRole, orgMember},
+		Scope:        rbac.ScopeAll,
+	}.WithCachedASTValue()
+}