Add vote instruction count metrics

[HaoranYi]

Problem

In solana-labs#24696, we removed the processed vote instruction counters because of spamming.

However, it is useful to know how many vote instructions per second are processed by the validator.

Summary of Changes

Add vote instruction counter metrics.

Fixes #

[mergify]

The Firedancer team maintains a line-for-line reimplementation of the
native programs, and until native programs are moved to BPF, those
implementations must exactly match their Agave counterparts.
If this PR represents a change to a native program implementation (not
tests), please include a reviewer from the Firedancer team. And please
keep refactors to a minimum.