fa32cc0 doc: Remove fee delta TODO from txmempool.cpp (MarcoFalke)

Pull request description:

  This refactor request was added in commit eb30666, though it didn't explain why the refactor is needed and what the goal is. Given that this wasn't touched for more than 5 years, it doesn't seem critical. Generally, non-trivial `TODO`s make more sense as GitHub issues, so that they can be discussed and triaged more easily.

ACKs for top commit:
  laanwj:
    Code review ACK fa32cc0

Tree-SHA512: 6629fef543e815136c82c38aa8ba2c4de68a5fe94c6954f2559e468f7e59052e02dd7c221d3b159be0314eaf0dbb18f74814297c58f76e2289c47e8d4f49be4e

4444dbf gui: Remove un-actionable TODO (MarcoFalke)

Pull request description:

  With encryption turned on by default for all wallets in consideration (bitcoin#18889), I believe that wallet decryption will not be implemented ever or at least any time soon. So remove that TODO comment for now. If deemed important, a brainstorming issue can be opened instead.

  Also remove some TODOs in the RPC console, which I don't understand. Maybe the gui was meant to show the debug log interactively? In any case, if deemed important, this should be filed as a brainstorming feature request, so that trade-offs of different solutions can be discussed.

ACKs for top commit:
  laanwj:
    Thanks. ACK 4444dbf
  achow101:
    ACK 4444dbf

Tree-SHA512: f7ddb37a14178f575da5409ea1c34e34bde37d79b2b56eaaf606a069e2b91c9d7b734529f5c68664b2fa5aa831117c8d19cce823743671cd6c31b81d68b8c70c

fabea6d net: Run clang-format on protocol.h (MarcoFalke)
facdeea net: Remove un-actionable TODO (MarcoFalke)

Pull request description:

  The first commit removes a TODO that is infeasible to solve. Currently, most (de)serializable classes in Bitcoin Core have public members. For example `CMessageHeader`, `FlatFilePos`, `CBlock`, `CTransaction`, `CCoin`, ...

  So either this TODO comment should apply to all classes or to none. Fix that discrepancy by removing it from the source code for now. If deemed important, the TODO can be discussed in a brainstorming issue later.

  Also run clang format on the header file in a new commit. Happy to drop this commit if it is too controversial, but I think it is trivial to review and makes the workflow of developers using clang-format-diff easier.

ACKs for top commit:
  practicalswift:
    ACK fabea6d
  naumenkogs:
    ACK fabea6d. Not sure why that TODO was there in the first place, but Marco's justification seems correct.
  hebasto:
    ACK fabea6d, agree with both changes: removing TODO and applying the `clang-format-diff.py`.

Tree-SHA512: b79ae07be27e5a40fc9f411a5e9ae91aecb2fdedbcbf74699614a1004f4ef816bf396903ec6c06eb1395fd83a2047620c7583acbaadfb8c4e613319a63062c3c