refactor: replace context.Background() with t.Context()/b.Context() in tests (#7352)

Based on the Go version we currently use, the dependency already
supports 1.24+, which allows using `t.Context()` and `b.Context()` in
unit tests and benchmarks respectively.

- Enable `context-background` and `context-todo` in
[`usetesting`](https://golangci-lint.run/docs/linters/configuration/#usetesting)
- Adjust the code to support linter detection

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
Co-authored-by: Tyler Yahn <codingalias@gmail.com>
Co-authored-by: Damien Mathieu <42@dmathieu.com>

trace/context_test.go

@@ -45,27 +45,27 @@ func TestSpanFromContext(t *testing.T) {
 		},
 		{
 			name:         "background context",
-			context:      context.Background(),
+			context:      t.Context(),
 			expectedSpan: emptySpan,
 		},
 		{
 			name:         "local span",
-			context:      ContextWithSpan(context.Background(), localSpan),
+			context:      ContextWithSpan(t.Context(), localSpan),
 			expectedSpan: localSpan,
 		},
 		{
 			name:         "remote span",
-			context:      ContextWithSpan(context.Background(), remoteSpan),
+			context:      ContextWithSpan(t.Context(), remoteSpan),
 			expectedSpan: remoteSpan,
 		},
 		{
 			name:         "wrapped remote span",
-			context:      ContextWithRemoteSpanContext(context.Background(), remoteSpan.SpanContext()),
+			context:      ContextWithRemoteSpanContext(t.Context(), remoteSpan.SpanContext()),
 			expectedSpan: wrappedSpan,
 		},
 		{
 			name:         "wrapped local span becomes remote",
-			context:      ContextWithRemoteSpanContext(context.Background(), localSpan.SpanContext()),
+			context:      ContextWithRemoteSpanContext(t.Context(), localSpan.SpanContext()),
 			expectedSpan: wrappedSpan,
 		},
 	}