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/auto_test.go

@@ -171,7 +171,7 @@ func TestTracerStartPropagatesOrigCtx(t *testing.T) {
 	var key ctxKey
 	val := "value"
 
-	ctx := context.WithValue(context.Background(), key, val)
+	ctx := context.WithValue(t.Context(), key, val)
 	ctx, _ = newAutoTracerProvider().Tracer(tName).Start(ctx, "span.name")
 
 	assert.Equal(t, val, ctx.Value(key))
@@ -181,7 +181,7 @@ func TestTracerStartReturnsNonNilSpan(t *testing.T) {
 	t.Parallel()
 
 	tr := newAutoTracerProvider().Tracer(tName)
-	_, s := tr.Start(context.Background(), "span.name")
+	_, s := tr.Start(t.Context(), "span.name")
 	assert.NotNil(t, s)
 }
 
@@ -189,7 +189,7 @@ func TestTracerStartAddsSpanToCtx(t *testing.T) {
 	t.Parallel()
 
 	tr := newAutoTracerProvider().Tracer(tName)
-	ctx, s := tr.Start(context.Background(), "span.name")
+	ctx, s := tr.Start(t.Context(), "span.name")
 
 	assert.Same(t, s, SpanFromContext(ctx))
 }
@@ -199,7 +199,7 @@ func TestTracerConcurrentSafe(t *testing.T) {
 
 	const goroutines = 10
 
-	ctx := context.Background()
+	ctx := t.Context()
 	run := func(tracer Tracer) <-chan struct{} {
 		done := make(chan struct{})
 
@@ -377,7 +377,7 @@ func TestSpanCreation(t *testing.T) {
 		},
 	}
 
-	ctx := context.Background()
+	ctx := t.Context()
 	for _, tc := range testcases {
 		t.Run(tc.TestName, func(t *testing.T) {
 			if tc.Setup != nil {
@@ -1071,7 +1071,7 @@ func TestSpanConcurrentSafe(t *testing.T) {
 		go func(tracer Tracer) {
 			defer close(done)
 
-			ctx := context.Background()
+			ctx := t.Context()
 
 			var wg sync.WaitGroup
 			for i := range nSpans {