Copies scripts out of the GSI monitor repo into global workflow.

Refs: NOAA-EMC#967

Updates the new GSI monitor scripts to incorporate some of the improvements
already added to other workflow scripts:
- Let preamble handle script entry/exit messages and bash set
- Replace backticks with $( ) for subshells
- Remove env prints

Refs: NOAA-EMC#967

`ush/radmon_ck_stdout.sh` was being ignored, but it was not even being
linked by the link script anymore, so the ignore is unnecessary.

Refs: NOAA-EMC#967

One radmon script is needed but was not previously linked, so it hadn't
been added to the repository.

Refs: NOAA-EMC#967

After moving the GSI monitor scripts to workflow, several of the scripts
would fail because set -eu is on, either due to undefined variables or
trying to operate on non-existent files. This corrects some of those issues.

Some of the non-existent files were globs, for these the bash built-in
`compgen -G` is used to check if it resolves to any files.

Refs: NOAA-EMC#967

Removes unused mail options from radmon scripts. Also an outdated comment.

Refs: NOAA-EMC#967