ci: fix Linux apt package install (stale apt lists + poisoned cache), fix cargo msrv find

[nicoburns]

Summary

All Linux CI jobs (lint, tests, release tests, bundle, docs, min-deps) currently fail at glib-sys with glib-2.0.pc not found.

Cause (from job logs): the runner image's apt lists are stale — they point at xdg-desktop-portal_1.18.4-1ubuntu2.24.04.2, which has been superseded by .3 and removed from the mirror pool, so the install 404s. awalsh128/cache-apt-pkgs-action's own refresh is sudo apt-fast update ... || true (silently no-op'd here), and its install step doesn't fail the job: it installed 0 packages and then saved that empty result to the cache key. Every later run restores the poisoned empty cache, so nothing is installed and every Linux job fails identically regardless of PR contents.

Fix:

• Add an explicit sudo apt-get update step immediately before every cache-apt-pkgs-action use (same if: guards where present), so the package index is fresh and the install succeeds.
• Bump every cache-apt-pkgs-action version: 1.0 → 1.2 (matrix key prefixed 1.2-) to evict the poisoned caches (1.1 was also poisoned by the first iteration of this PR).

Also fixes the Find MSRV on verify failure step, which errored with unrecognized subcommand 'cargo': cargo-msrv 0.19 requires the explicit find subcommand:

-cargo msrv --output-format json -- cargo check
+cargo msrv --output-format json find -- cargo check

Not addressed: Playwright job flakiness (known).

Link to Devin session: https://dioxus.staging.devinenterprise.com/sessions/2cd42a65391e46a19e32f06831e90d22
Open in Devin Desktop: https://dioxus.staging.devinenterprise.com/desktop/session/2cd42a65391e46a19e32f06831e90d22?variant=devin-insiders
Requested by: @nicoburns

[staging-devin-ai-integration]

I'll fix CI failures and address comments from users with write access that start with 'Devin'.

• Disable automatic comment, CI, and merge conflict monitoring