Re-enable rust, fix ubuntu 18 failure

[samansmink]

restore rust-based extension builds

restores building rust-based extensions by reverting the changes from #42 in favor of setting ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true

We should properly fix this asap as ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION could be removed at any time.

Add CI job to test PRs to this repo

This PR also adds a CI job to test this repo by building https://github.com/duckdb/extension-template and https://github.com/duckdb/duckdb_delta using this version of the ci tools.

Fixes ubuntu 18 failures

Fixes failures like this:

There’s nothing that PPA owners can do about this for now, as the key is fully controlled internally by Launchpad.
 More info: https://launchpad.net/~git-core/+archive/ubuntu/ppa
Error: retrieving gpg key timed out.

in the ubuntu18 setup script by completely removing that. In the process I stripped various other things that are old and unused.

Future work

• Re-enable the fix from Unroll logic out of github action and into docker + script #42 in a cleaner way which support rust builds.

• Further clean up the Linux based CI. As Ubuntu18 and manylinux2014 are getting long in the tooth, we should move towards a setup where we are less likely to suffer from breakage as github architectures. All linux builds should likely just manually run the build inside docker container then upload the artifacts outside of docker

[carlopi]

Looks good!

[samansmink]

failure is unrelated