Backport fixes for Git v2.48

This merge request backports a couple of patch series into Git v2.48 that have already been merged upstream.

The first set of backports fixes a couple of regressions introduced by the new reflog migration code. These fixes fix the migration logic itself as well as an uninitialized-memory read introduced is the reftable backend. These backports include:

• ps/reflog-migration-with-logall-fix at a0bea097 (refs: fix migration of reflogs respecting "core.logAllRefUpdates", 2025-01-22).
• kn/reflog-migration-fix at bc67b4ab (reftable: write correct max_update_index to header, 2025-01-15).
• kn/reflog-migration-fix-fix at f11f0a5a (refs/reftable: fix uninitialized memory access of max_index, 2025-01-27).

The second set of backports includes fixes for the Meson build system as well as a backport of the new zlib-ng backend. These backports ensure that we can start dogfooding the Meson build system and roll out zlib-ng to production. These backports include:

• ps/meson-weak-sha1-build at 6a0ee54f (meson: provide a summary of configured backends, 2024-12-30).
• tc/meson-use-our-version-def-h at 4771501c (meson: ensure correct version-def.h is used, 2025-01-14).
• sj/meson-doc-technical-fix at 1dca492e (meson: fix missing deps for technical articles, 2025-01-14).
• ps/build-meson-fixes at 7304bd2b (ci: wire up Visual Studio build with Meson, 2025-01-22).
• ps/zlib-ng at 78cdeed4 (ci: make "linux-musl" job use zlib-ng, 2025-01-28).

All of these patch series have been merged upstream already and will be released as part of Git v2.49.