ci: set typos action to v1 tag

[bkircher]

• ci: set typos action to v1 tag

• ci: pin cargo-pgrx version to match Cargo.toml

• ci: fix pgrx cache to avoid rebuilding Postgres

The cache guard checked ~/.pgrx/pg18/ but pgrx installs to
~/.pgrx/18.2/, so the check always failed and Postgres was
compiled from source on every run despite a cache hit. Use a
glob to match the actual install path.

Also key the cache on the pgrx version instead of the full
Cargo.lock hash, since ~/.pgrx only changes when the pgrx or
Postgres major version changes.

• ci: extract pgrx version into a workflow variable

Avoid duplicating the version string across the install step
and the cache key. A single env.PGRX_VERSION variable makes
future version bumps a one-line change.

• Bump pgrx from 0.16.1 to 0.17.0

• Simplify base62_encode and remove dead code

pgrx::Uuid is always 16 bytes, so the length check and
InvalidInput error variant were unreachable. Also replace
the if-let block with the ? operator and use expect for the
infallible UTF-8 conversion of base62 output.

• ci: cache cargo-pgrx binary across runs

We have now three caches that are hit perfectly:

1. cargo-pgrx binary — cargo-pgrx-Linux-0.17.0 — restored in ~2s, install step skipped
2. pgrx home — pgrx-Linux-0.17.0-pg18 — restored in ~5s, Postgres init skipped
3. cargo build — handled by Swatinem/rust-cache

That's ~8 minutes of compilation saved on every cached run.