testing/zig: upgrade to 0.12.0

not rebuilt:

• fbp - discontinued, should be removed? https://git.sr.ht/~mil/fbp
• limkd - no commits for a year, is it still maintained? https://git.sr.ht/~mil/limkd
• linuxwave - https://github.com/orhun/linuxwave/pull/8
• river - vendoring has layers
• waylock
• zls