util: Explain why the path is cached #16300

The rationale for caching the datadir is given as

    // This can be called during exceptions by LogPrintf(), so we cache the
    // value so we don't have to do memory allocations after that.

Since 8c2d695c4a45bdd9378c7970b0fcba6e1efc01f9, the debug log location is actually cached itself in m_file_path.

So explain that the caching is now only used to guard against disk access on each call. (See also #16255)

utACK fa69c3e6ca71800376761e264320c363f072dc2f. Good cleanup. Previous comment was confusing, and definitely not helpful if outdated.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #16273 (refactor: Remove unused includes by practicalswift)
• #15934 (Separate settings merging from parsing by ryanofsky)
• #15864 (Fix datadir handling by hebasto)

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 fa69c3e6ca71800376761e264320c363f072dc2f.

Fair enough, I liked the ambitiousness of getting rid of this code, but, this is a clear and non-controversial improvement ACK fa69c3e6ca71800376761e264320c363f072dc2f