metric: counter for cached queries executed in transaction

[Daksh-10]

Solves #1394

The changes increment the counter after checking if a cached query is sent upstream due to it being in a transaction.

The metric is exposed on http://127.0.0.1:6033/metrics

1. Create cache from Select * from tb1 where ID=1;
2.  Select * from tb1 where ID=1; (counter will not be updated)
3. Start transaction;
4. Select * from tb1 where ID=1; (counter will be updated)

[Daksh-10]

Hi @altmannmarcelo,
I updated the PR. What are your thoughts?