Remove broken and unused CDataStream methods #24253

The insert and erase methods have many issues:

• They are unused
• They are confusing and hard to read, as they implement "special cases" for optimization, that isn't needed
• They are broken (See #24231)
• Fixing them leads to mingw compile errors (See #24231 (comment))

Fix all issues by removing them

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #24231 (streams: Fix read-past-the-end and integer overflows 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.

ACK, though I'd put the first commit last so the other two can be backported* cleaner.

Also confirmed 21.x doesn't use these functions either, so a real fix isn't needed either.

* I don't see a need to backport them, though.

I don't see a need to backport them, though.

Indeed, there is no need to backport, so I am going to leave as is for now.

Code review ACK fa1b227a727a5056c6fbc7e4f33c19aeb5207718 Nice cleanup!