Is your feature request related to a problem? Please describe.
Now that Vault Agent metrics have been released in v1.10.0 (hashicorp/vault#13675), the injector needs a way to enable and configure them. There is a strong need for those using the Vault Injector in production to have insights on Vault authentication/ connection issues from the injected agent.

Describe the solution you'd like
A means to configure metrics on Vault Agent via Injector annotations and environment variables

Describe alternatives you've considered
The "vault.hashicorp.com/agent-configmap" annotation allows for mounting a custom Agent config in place of relying on annotations. Redesigning our existing pipeline to generate a unique configmap for each service's agent, just to enable metrics configuration, is less than ideal though.