Enhancement: Make installer release process more automated and idempotent

**Summary**
I propose that the process of composing and releasing installers be made both more automated, and more idempotent.

**Details**
Creating four large PRs with checksums (etc etc) invites error and takes time. Also, the resulting installer creation job has been identified as being "clunky", and unable to be rerun if it fails. Instead, various manual changes need to be made before the job can be restarted.

For this reason, and others, I propose that this process be reviewed for a greater degree of automation and idempotency.

**Background**
During a recent Release Champion meeting (minuted [here](https://github.com/adoptium/adoptium/issues/235)), the installer creation and release process was identified as one of the blockers to a quick and efficient release. Also, if something goes wrong during certain parts of the process, excessive effort is required to restore things to a state where the process can be resumed.

**Relevant Parties**
@gdams, or one of his associates, may be working on increased automation for this process. As such, this may be a duplicate of another issue.

Any thoughts George?

Start by reviewing the installer creation and release process described in this issue and the Release Champion meeting notes in adoptium/adoptium#235. Identify the manual steps, failure recovery requirements, and existing automation before defining a scoped change; done would mean a more automated, rerunnable, and idempotent release process.

Written by the indexing model from the issue text.