feat: support merging non-string sections

[karolzwolak]

Implements #838.

[karolzwolak]

This is WIP but I wanted to get some feedback.
Things left to do:

• update all the types and docs when necessary (this is only partially done atm)
• add clearer separation between string and non-string sections in code to be less confusing and more efficient

[davidlattimore]

Awesome!

Regarding doing lots of renames of string-merging to section-merging, I'd say don't worry too much. I'd say probably update the comment at the top of string_merging.rs to say that the code also handles merging of non-string sections. If we do decide to do lots of renames, they should probably be done in a separate PR, but it's probably fine to leave things as you've got them.

Anyway, I think this is basically good to merge.

[karolzwolak]

Glad to hear that. I added a few commits that addressed you comments and did minor refactor and improved docs.

[karolzwolak]

The ubuntu 24.04 on aarch64 check failure looks like some CI issue.

Get:12 http://ports.ubuntu.com/ubuntu-ports noble-updates/universe arm64 Packages [1865 kB]
Err:12 http://ports.ubuntu.com/ubuntu-ports noble-updates/universe arm64 Packages
  File has unexpected size (1864981 != 1864881). Mirror sync in progress? [IP: 91.189.91.103 80]
  Hashes of expected file:
   - Filesize:1864881 [weak]
   - SHA256:35183757127012ad30f38ba2ca56973aadbbb45f0905438203b93cfce75e4630
   - SHA1:f435e67f90a4dfa54287c3e31b173e55f6653ca9 [weak]
   - MD5Sum:637252ef5d5162dd76d0f6117f8a673a [weak]
  Release file created at: Sun, 16 Nov 2025 10:56:23 +0000
Fetched 34.6 MB in 4s (8310 kB/s)
Reading package lists...
E: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/noble-updates/universe/binary-arm64/Packages.gz  File has unexpected size (1864981 != 1864881). Mirror sync in progress? [IP: 91.189.91.103 80]
   Hashes of expected file:
    - Filesize:1864881 [weak]
    - SHA256:35183757127012ad30f38ba2ca56973aadbbb45f0905438203b93cfce75e4630
    - SHA1:f435e67f90a4dfa54287c3e31b173e55f6653ca9 [weak]
    - MD5Sum:637252ef5d5162dd76d0f6117f8a673a [weak]
   Release file created at: Sun, 16 Nov 2025 10:56:23 +0000
E: Some index files failed to download. They have been ignored, or old ones used instead.
Error: Process completed with exit code 100.

[mati865]

Yeah, AArch64 GHA runners do that sometimes.