Reduce third-party build script dependencies and reduce GITHUB_TOKEN perms in CI...

Reduce third-party build script dependencies and reduce GITHUB_TOKEN perms in CI (#541)

* Reduce dependence on third-party build scripts in release pipeline

This removes one third-party build script from the release
pipeline for the release tar.gz, though one is still used in the
now-separate netlify deploy.

* Reduce GITHUB_TOKEN perms in actions when using 3rd party scripts

This avoids allowing third parties to arbitrarily overwrite the
repository.

* Replace PGP signing action with the bash script from the same

The PGP signing action ultimately just calls gpg with arguments
set in
https://github.com/actionhippie/gpgsign/blob/v1/overlay/usr/local/bin/entrypoint
so its rather trivial to simply take the required arguments and
put them directly in CI.

This is substantially safer than the PGP signing action used as the
action currently downloads, unverified and un-pinned, a docker
image in order to access PGP.