refactor: Make CTransaction constructor explicit #25694

It involves calculating two hashes, so the performance impact should be made explicit.

Also, add the module to iwyu.

ACK fa2247a9f9754d90ea60f254f6c0ed881c55772b, I have reviewed the code and it looks OK, I agree it can be merged.

ACK fa2247a9f9754d90ea60f254f6c0ed881c55772b. In my understanding, these changes disable copy-initialization of CTransaction to avoid potentially hashing twice.

On a related note, should we make all single-argument constructors explicit ? https://github.com/isocpp/CppCoreGuidelines/blob/6f27719b2b994d1304f78194dc7824e4ddeea5f5/CppCoreGuidelines.md#c46-by-default-declare-single-argument-constructors-explicit

In my understanding, these changes disable copy-initialization of CTransaction to avoid potentially hashing twice.

Not sure what you mean, but this should not change any constructor or code logic. This simply forces devs to write CTransaction at least once if they want to construct one.

On a related note, should we make all single-argument constructors explicit ? https://github.com/isocpp/CppCoreGuidelines/blob/6f27719b2b994d1304f78194dc7824e4ddeea5f5/CppCoreGuidelines.md#c46-by-default-declare-single-argument-constructors-explicit

Probably not, as the url you link to advises against that.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #17529 (rpc: Faster getblock using PureBlock by MarcoFalke)

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.