revert: block copy program

Was done on #157, the feature is ineffective as it can be disabled if
supautils is not on shared_preload_libraries (which is not recommended
as a supautils upgrade would require a cluster restart).

chore: supautils-style

refactor: use clang-format style

You can run this with:

```bash
supautils-style
```

The style is also checked on CI.

ci: release .so instead

ci: release .so instead

ci: swap out arm-runner

refactor: clarify skip event trigger code

feat: compatibility with pg 18beta1

The `lowerstr` function was removed in favor of `str_tolower`

fix: compilation with standard PGXS target

Using the EXTENSION variable implicitly requires a .control file.

Also ensure `all` is the default target.

test: split extension custom scripts tests