chore: remove coder_secret Terraform integration (#25512)

Removes the coder_secret Terraform integration: the data.coder_secret
consumption path through provisionerdserver → provisioner.proto →
provisioner/terraform, the dynamic-parameter secret-requirement
validation, and the workspace-update / resolve-autostart surfaces that
depended on it. This is being done due to a product/feature direction
change (see PLAT-243). User-secret CRUD (DB, REST, CLI, UI, telemetry, audit)
and the agent-manifest secret-injection path are untouched.

The provisionerd API is bumped from v1.17 to v1.18 rather than rolled
back: v1.17 shipped in v2.33.x, so user_secrets field numbers are
reserved and the changelog documents both versions.

Generated with assistance from Coder Agents.

coderd/dynamicparameters/static.go

@@ -39,7 +39,7 @@ func (r *loader) staticRender(ctx context.Context, db database.Store) (*staticRe
 	}, nil
 }
 
-func (r *staticRender) Render(_ context.Context, _ uuid.UUID, values map[string]string, _ ...RenderOption) (*RenderResult, hcl.Diagnostics) {
+func (r *staticRender) Render(_ context.Context, _ uuid.UUID, values map[string]string) (*preview.Output, hcl.Diagnostics) {
 	params := r.staticParams
 	for i := range params {
 		param := &params[i]
@@ -52,10 +52,8 @@ func (r *staticRender) Render(_ context.Context, _ uuid.UUID, values map[string]
 		param.Diagnostics = previewtypes.Diagnostics(param.Valid(param.Value))
 	}
 
-	return &RenderResult{
-			Output: &preview.Output{
-				Parameters: params,
-			},
+	return &preview.Output{
+			Parameters: params,
 		}, hcl.Diagnostics{
 			{
 				// Only a warning because the form does still work.