Clean up historical CI config

[ofalvai]

History and background context:

• Azure CI config is the original one. It also contains internal Microsoft tooling that is no longer relevant.
• GHA config was added in f149a12, but it wasn't a 1:1 migration
• The jobs ios-old-arch-test and android-new-arch-test are broken since Add Rn 0.82.1 support codemagic-ci-cd/react-native-code-push#33, which dropped RN old arch support.

Changes

• Delete Azure CI pipeline configs, but
• Set up a quick lint job that runs first and doesn't involve emulators/simulators
• Make the Android and iOS test jobs actually work. On the Android side, use the de-facto https://github.com/ReactiveCircus/android-emulator-runner instead of the shell script tweaks in the old Azure config.
• Set up tool version pinning via Mise and mise.toml.
• Runners (runs-on): set up some org-wide hosted large runners. On the Linux side, these are needed because of nested virtualization, and the default macOS runners are too weak for our stuff.

Out of scope

• Optimize CI performance or reliability: later
• Revisit Node/JDK/etc tool version, do upgrades: later