Shuttle: v0.50.0 update

Fixed a bug where RUST_LOG was overridden in local runs with the new shuttle CLI in #1930

Other updates

Increased MSRV of the Shuttle crates to 1.81
The version of libsql in the shuttle-turso crate has been upgraded from 0.3.1 to 0.6.0.

@geofmureithi updated the shuttle-cron example in shuttle-hq/shuttle-examples#194
@Aditya-PS-05 replaced the unmaintained proc-macro-error crate with proc-macro-error-2 in #1921
@c-git fixed a typo in the shuttle-service docs in #1935
@sentinel1909 upgraded libsql in shuttle-turso in #1940 and shuttle-hq/shuttle-examples#197

Refer to the upgrading docs for how to upgrade your projects.

fix: cargo-audit version by @jonaro00 in #1919
added proc-macro-error2 dependency by @Aditya-PS-05 in #1921
shuttle.dev cleanup by @jonaro00 in #1920
fix: admin and cli fixes by @jonaro00 in #1922
feat: deprecate new project creation by @oddgrd in #1931
docs: typo fix by @c-git in #1935
feat: bump common msrv to 1.81, our images to 1.83 by @oddgrd in #1942
feat: add xl and xxl compute tiers by @oddgrd in #1946
feat: update rds resource type for new platform compatibility by @oddgrd in #1945
improvement: update the Turso resource to use libsql 0.6.0 by @sentinel1909 in #1940
feat: deprecate new deployments by @oddgrd in #1934
fix(cargo-shuttle): don't override user provided RUST_LOG on local run by @jonaro00 in #1930
chore: prepare v0.50.0 release by @oddgrd in #1948

Full Changelog: v0.49.0...v0.50.0