Fix CI failures: import order and test expectations

This commit fixes two categories of CI failures:

1. Import Order (goimpi lint failures - 24 errors):
   - Fixed mdatagen templates to follow stdThirdPartyLocal scheme
   - Separated standard library, third-party, and local imports with blank lines
   - Modified templates: package_test.go.tmpl, component_test.go.tmpl,
     metrics.go.tmpl, metrics_test.go.tmpl, logs.go.tmpl, logs_test.go.tmpl
   - Regenerated all mdatagen generated files with correct import order
   - Applied goimports -local go.opentelemetry.io/collector to all generated files

2. Test Expectations (display_name field):
   - Updated loader_test.go to expect "Sample Receiver" instead of "Sample"
   - This matches the actual display_name value in metadata.yaml

All goimpi lint checks now pass.
All mdatagen tests pass.

Fixes #14115

Author: thc1006

cmd/mdatagen/generated_package_test.go

@@ -47,7 +47,7 @@ func TestLoadMetadata(t *testing.T) {
 				GithubProject:        "open-telemetry/opentelemetry-collector",
 				GeneratedPackageName: "metadata",
 				Type:                 "sample",
-				DisplayName:          "Sample",
+				DisplayName:          "Sample Receiver",
 				SemConvVersion:       "1.9.0",
 				PackageName:          "go.opentelemetry.io/collector/cmd/mdatagen/internal/samplereceiver",
 				Status: &Status{