Replace 3rd party grpc-healh-probe binary in probes invoked internally

[zolug]

Is your feature request related to a problem? Please describe.
In Meridio probes might rely on multiple so called subservice states to report their serving status.
Some of these subservices might require running 3rd party grpc-health-probe binary to check an associated
gRPC server's serving state. The attestation due to periodically forking a new process and fetching credentials for such a probe introduces additional CPU load on Spire when checking a TLS server with SPIFFE issued credentials.

Describe the solution you'd like
In case of subservices replace the 3rd party binary grpc-health-probe with a health client contained within the calling process,
and avoid constant attestation by Spire agents whenever the health client Checks a TLS server with SPIFFE issued credentials.

Describe alternatives you've considered
NA

Additional context
NA