Remove direct github.com/pkg/errors usage

[MukundaKatta]

Description

• replace direct github.com/pkg/errors imports with the standard library errors and fmt
• preserve wrapping with %w where callers rely on errors.Is or errors.As
• keep nil-wrap behavior in requeue paths that previously depended on errors.Wrap(nil, ...) returning nil
• move github.com/pkg/errors from direct to indirect in go.mod, since it is still pulled in transitively

Fixes #654

Testing

• go test ./internal/service/vmservice ./internal/inject ./pkg/cloudinit ./pkg/ignition ./pkg/kubernetes/ipam ./pkg/proxmox/goproxmox ./pkg/scope
• go test ./... (fails locally because envtest cannot find /usr/local/kubebuilder/bin/etcd; non-envtest packages run and pass)
• git diff --check