feat(txpool/tracker): make tracker fb aware

[wlawt]

Changes

• Introduces a new metric fb_inclusion_duration
• Records the metric when it sees the txhash in a PendingBlock. NOTE: on FB inclusion, it does not remove the TxHash in the Tracker's cache. This is to let us record when its included in the canonical block for the other existing metrics.
• Moved build_eip1559_tx into shared test_utils

TODO

• Add a unit test that invokes track_flashblock_transactions

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[wlawt]

AFAIK, a transaction sent to us is sent to both the builder and the mpool, at the same time. Therefore, this should be accurate, as we'll start tracking right when we see it in the mpool to when it's in a PendingBlock