refactor(errs): migrate from gperr.Error to standard Go error interface

This is a large-scale refactoring across the codebase that replaces the custom
`gperr.Error` type with Go's standard `error` interface. The changes include:

- Replacing `gperr.Error` return types with `error` in function signatures
- Using `errors.New()` and `fmt.Errorf()` instead of `gperr.New()` and `gperr.Errorf()`
- Using `%w` format verb for error wrapping instead of `.With()` method
- Replacing `gperr.Subject()` calls with `gperr.PrependSubject()`
- Converting error logging from `gperr.Log*()` functions to zerolog's `.Err().Msg()` pattern
- Update NewLogger to handle multiline error message
- Updating `goutils` submodule to latest commit

This refactoring aligns with Go idioms and removes the dependency on
custom error handling abstractions in favor of standard library patterns.

internal/idlewatcher/errors.go

@@ -20,7 +20,7 @@ func (e *watcherError) Error() string {
 }
 
 func (w *Watcher) newWatcherError(err error) error {
-	if errors.Is(err, causeReload) {
+	if errors.Is(err, errCauseReload) {
 		return nil
 	}
 	if wErr, ok := err.(*watcherError); ok { //nolint:errorlint
@@ -44,7 +44,7 @@ func (e *depError) Error() string {
 }
 
 func (w *Watcher) newDepError(action string, dep *dependency, err error) error {
-	if errors.Is(err, causeReload) {
+	if errors.Is(err, errCauseReload) {
 		return nil
 	}
 	if dErr, ok := err.(*depError); ok { //nolint:errorlint