Add GitHub action to push latest sha release as new semver to internal PyPI about dbt-redshift

[VersusFacit]

MVP ready to go in my forked repo. Successful build and upload job (no testing yet, see Slack for discussion about testing internal releases )

The 1.8.0b1 was there. The 1.8.0b2 was automated.

Blocked my the following convos happening in Slack:

1. Emily and I will discuss how to professionalize
2. Dash and I will harden the security if needed from here (may not be!)
3. Michelle and Chenyu will align with us on the final semver scheme for Mantle's needs, although I have a dummy script already written for doing a build number semver scheme

 1. Query AWS for latest release
 2. trim off its build number
 3. create release number <current version>+<last build number+1> 
 4. rename the wheel and tar gz with this release number <major>.<minor>.<release>b<beta number>+<build no.>

[martynydbt]

When do we expect this to be unblocked?