optimization: reserve memory allocation for transaction inputs/outputs

[l0rinc]

Reserved memory for the transaction inputs and outputs.

Split out of https://github.com/bitcoin/bitcoin/pull/30050/files#r1597631104

[DrahtBot]

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Reviews

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Type	Reviewers
ACK	TheCharlatan
Concept ACK	josibake
Stale ACK	theuni

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #24128 (wallet: BIP 326 sequence based anti-fee-snipe for taproot inputs by maflcko)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[theuni]

Concept ACK

[josibake]

Concept ACK

I noticed you have benchmarks, would be nice to have the comparison of old vs new in the PR description.

[l0rinc]

Thanks for the review @josibake, I've added the conclusions of the benchmarks to the commit message (but copied it to the PR description as well now), can you please check if ebf8667 answers your questions?

@theuni, appreciate your previous reviews and insights, please take a look at the changes I did since.

[theuni]

Changes look good. The bench is not really useful though, because it's testing things that aren't in our code.

I believe @josibake was asking for a bench that demonstrates a before/after of CreateTransactionInternal. I'm guessing that's not really feasible though, so I think it's enough to use your bench numbers without actually committing it.

[l0rinc]

Moved the benchmark out to https://gist.github.com/paplorinc/812007eef71d5285be0654375ea3e03e

[theuni]

utACK db2a31c

[TheCharlatan]

ACK ec585f1