refactor(promslog): make NewNopLogger() wrapper around New() (#783)

* refactor(promslog): make `NewNopLogger()` wrapper around `New()`

While discussing the fix for prometheus/prometheus#16466, it was pointed
out that our `promslog.NewNopLogger()` convenience function would
benefit from using the same logic used when initializing loggers with
`promslog.New()`. By refactoring NewNopLogger to wrap New, it inherits
that same setup logic.

Signed-off-by: TJ Hoplock <[email protected]>

* fix(promslog): don't set NewNopLogger to debug level

Signed-off-by: TJ Hoplock <[email protected]>

---------

Signed-off-by: TJ Hoplock <[email protected]>

Author: tjhop

promslog/slog.go

@@ -266,5 +266,5 @@ func New(config *Config) *slog.Logger {
 // NewNopLogger is a convenience function to return an slog.Logger that writes
 // to io.Discard.
 func NewNopLogger() *slog.Logger {
-	return slog.New(slog.NewTextHandler(io.Discard, nil))
+	return New(&Config{Writer: io.Discard})
 }