fix(operator): consistent pod service monitors reconcilor app labels

[michaelcheah]

What this PR does / why we need it:
The default matchLabel configs for Prometheus podmonitors do not match what is configured by the SeldonRuntime operator for several resources.

This PR:

1. Fixes the labels so that they are consistent across all resources, i.e. all label use app.kubernetes.io/name key instead of app to reference seldon components
2. The component name seldon-mesh is outdated and is updated to seldon-envoy.
3. The server metrics port for the default mlserver is not defined (it is defined for the triton server). We expose it on port 8082 which is the default for mlserver

Which issue(s) this PR fixes:
Fixes #5071

Special notes for your reviewer: