v1.18: forwarder uses working bank as filter (backport of #1129)

[mergify]

Problem

• Forwarder uses root_bank for checking transactions
• This will cause non-rooted blockhashes to get filtered out

Summary of Changes

• use working_bank instead

Fixes #

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This is an automatic backport of pull request #1129 done by [Mergify](https://mergify.com).

[bw-solana]

Note: This problem was discovered when trying to fetch a blockhash with confirmed commitment level for the ping client. Latency jumped up because these transactions were getting filtered out by the staked node forwarder until the blockhash became rooted.

These changes were run on the ping staging staked node (3gG) and confirmed to resolve the ping latency issue:

In graph above, here is what was running:

• Left side = using finalized blockhash. Good latency because nothing gets filtered
• Middle = using confirmed blockhash. Bad latency because we filter transactions for ~10 seconds
• Right = using confirmed blockhash. Good latency because filtering behavior was modified by this change.