fix(credential-provider): check empty mirror mapping and add debugging info

[mainred]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Run the binary will return error log Invalid registry mirror format without real harm since registryMirrorStr defaults to emtpy.
Fix this by checking the emptiness of registryMirrorStr and return when it's empty.
Besides this change, I added 3 small but debug-friendly changes in this PR to reduce the cherry-pick PR numbers.

• add klog verobse level flag -v
• add version flag --version
• add debug level log for correlationID.

Tests

• verbose log

The acr credential provider is responsible for providing ACR credentials for kubelet

Usage:
  acr-credential-provider configFile [flags]

Flags:
  -h, --help                           help for acr-credential-provider
      --log-flush-frequency duration   Maximum number of seconds between log flushes (default 5s)
  -r, --registry-mirror string         Mirror a source registry host to a target registry host, and image pull credential will be requested to the target registry host when the image is from source registry host
  -v, --v Level                        number for the log level verbosity
      --version                        version for acr-credential-provider
      --vmodule moduleSpec             comma-separated list of pattern=N settings for file-filtered logging (only works for the default text log format)

• print version

/var/lib/kubelet/credential-provider/acr-credential-provider --version
acr-credential-provider version v1.31.0-689-g2ca98fff7

• correlationID debug log

:\"qingchuanhao.azurecr.io/nginx:v1\"}" | ./azure-acr-credential-provider /etc/kubernetes/azure.json -v 9
I0317 22:32:35.090733 3420293 azure_credentials.go:205] discovering auth redirects for: qingchuanhao.azurecr.io
I0317 22:32:35.383245 3420293 azure_credentials.go:212] exchanging an acr refresh_token
I0317 22:32:35.398506 3420293 azure_acr_helper.go:180] correlationID: [72f5cc8e-aabc-4535-8957-eacd486e5e25]
{"kind":"CredentialProviderResponse","apiVersion":"credentialprovider.kubelet.k8s.io/v1","cacheKeyType":"Registry","cacheDuration":"5m0s","auth":{"*.azurecr.*":{"username":"","password":""},"qingchuanhao.azurecr.io":{"username":"00000000-0000-0000-0000-000000000000","password":"***"}}}

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

fix(credential-provider): check empty mirror mapping and add debugging info

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[mainred]

/test pull-cloud-provider-azure-e2e-ccm-vmss-capz

[mainred]

ping @andyzhangx @feiskyer to take a look.

[andyzhangx]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andyzhangx, mainred

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [andyzhangx]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment