Adds transaction metrics for accounts & data loaded/stored

[brooksprumo]

Problem

While processing transactions, we track metrics related to how long it takes to load and store accounts, but not the number of accounts[^1] nor the amount of account data.

[^1]: Caveat: We do track the number of accounts that are passed to message processing, "execute_details_total_account_count", which matches the number of accounts loaded. So this PR adds a currently-redundant datapoint for number of loaded accounts. I can remove that if desired. Is there something similar on the store-side? I.e. a number-of-modified-accounts-to-be-stored?

Summary of Changes

Add metrics for the number of accounts and amount of account data loaded and stored during transaction processing.

Here's an example of the new metrics:

number of accounts

account data

[codecov[bot]]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (c6c2340) 81.6% compared to head (001acc4) 81.6%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #34718   +/-   ##
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  Coverage    81.6%    81.6%           
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  Files         830      830           
  Lines      224837   224866   +29     
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+ Hits       183505   183564   +59     
+ Misses      41332    41302   -30     

[brooksprumo]

Rebased to address merge conflicts.

[willhickey]

This repository is no longer in use. Please re-open this pull request in the agave repo: https://github.com/anza-xyz/agave