core/txpool/blobpool: simplify the drop txs logic in blobpool module.

[mask-pp]

• Prealloc capacity for ids and nonces.
• Simplify the logic of dropping offend transactions.

[karalabe]

SGTM

[holiman]

This change makes the code a bit smaller, that much I grant, but IMO not more simple.
The pre-alloc of ids and nonces makes it a bit more brittle, even though it's arguably slightly more performant.

I'd personally rather close this PR than merge it, but I'll leave it open for someone else to decide

[karalabe]

The old code had a clearer intent, that's given. But I don't see anything wrong with the new one either and if it's ever so slightly less allocy, why not

[BigPoppas]

nice

[karalabe]

In light of the latest broken release due to small refactors for the sake of refactoring, we've decided to reject such changes from now on as their value is semi-limited and they always post a danger to potentially breaking something unforeseen.