chore: do not use sentinel errors when unneeded

- main reason being it's a burden to always define sentinel errors at global scope, wrap them with `%w` instead of using a string directly
- only use sentinel errors when it has to be checked using `errors.Is`
- replace all usage of these sentinel errors in `fmt.Errorf` with direct strings that were in the sentinel error
- exclude the sentinel error definition requirement from .golangci.yml
- update unit tests to use ContainersError instead of ErrorIs so it stays as a "not a change detector test" without requiring a sentinel error

internal/updater/resolver/parallel.go

@@ -2,7 +2,6 @@ package resolver
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"net/netip"
 )
@@ -34,11 +33,6 @@ type parallelResult struct {
 	IPs  []netip.Addr
 }
 
-var (
-	ErrMinFound     = errors.New("not enough hosts found")
-	ErrMaxFailRatio = errors.New("maximum failure ratio reached")
-)
-
 func (pr *Parallel) Resolve(ctx context.Context, settings ParallelSettings) (
 	hostToIPs map[string][]netip.Addr, warnings []string, err error,
 ) {
@@ -90,7 +84,7 @@ func (pr *Parallel) Resolve(ctx context.Context, settings ParallelSettings) (
 	failureRatio := float64(len(warnings)) / float64(len(settings.Hosts))
 	if failureRatio > settings.MaxFailRatio {
 		return hostToIPs, warnings,
-			fmt.Errorf("%w: %.2f failure ratio reached", ErrMaxFailRatio, failureRatio)
+			fmt.Errorf("maximum failure ratio reached: %.2f failure ratio reached", failureRatio)
 	}
 
 	return hostToIPs, warnings, nil