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/metrics/period/poller.go

@@ -3,7 +3,6 @@ package period
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 	"net/url"
 	"os"
 	"path/filepath"
@@ -196,7 +195,7 @@ func (p *Poller[T, AggregateT]) Start(parent task.Parent) {
 				if tickCount%gatherErrsTicks == 0 {
 					errs, ok := p.gatherErrs()
 					if ok {
-						gperr.LogError(fmt.Sprintf("poller %s has encountered %d errors in the last %s:", p.name, len(p.errs), gatherErrsInterval), errs)
+						log.Err(errs).Msgf("poller %s has encountered %d errors in the last %s:", p.name, len(p.errs), gatherErrsInterval)
 					}
 					p.clearErrs()
 				}