Only accept txs once synced

[benaadams]

Is a lot of additional work on processing blocks and adding tx in the txpool that is completely irrelevant until synced. Skip this extra work.

Effects all types of sync (snap, full, archive etc)

Changes

• Skip trying to add tx to txpool if not yet synced
• Don't process block events in txpool if not yet synced

Types of changes

What types of changes does your code introduce?

• Optimization

Testing

Requires testing

• Yes

If yes, did you write tests?

• Yes