Publish a few missed config metrics

[jayz22]

Description

These metrics were added last time(soroban config setting tx_max_size_bytes, ledger_max_txs_size_bytes, ledger_max_tx_count), but forgot to be published.
Also fixed a typo in a variable.

Checklist

• Reviewed the contributing document
• Rebased on top of master (no merge commits)
• Ran clang-format v8.0.0 (via make format or the Visual Studio extension)
• Compiles
• Ran all tests
• If change impacts performance, include supporting evidence per the performance document

[sisuresh]

r+ f725553