Simpler str_ns handling

[infotroph]

Description

This is a condensed implementation of the core ideas from #3324:

• If site settings already contain lat and lon, use those and do not attempt to look site location up from the db
• For met.process only, allow site id to be missing. If so, create an ID by pasting lat & lon together
• Always treat site id as character not numeric, but continue condensing Bety IDs (1000000772 => 1-772) as before

@Sweetdevil144 please review -- if you agree this is a sufficient replacement, merging this will close #3324.

Motivation and Context

We learned a lot about DB-free runs since starting work on #3324. It's now clear that for most cases we want to require the user to provide site IDs rather than generate them ourselves, meaning much of the complexity proposed in the existing PR is unneeded. Rather than try to unwind all the changes there, I've cherry-picked out the core commits here and updated the format of the latlon-based IDs for reduced ambiguity.

Review Time Estimate

• Immediately
• Within one week
• When possible

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• My name is in the list of CITATION.cff
• I agree that PEcAn Project may distribute my contribution under any or all of
  • the same license as the existing code,
  • and/or the BSD 3-clause license.
• I have updated the CHANGELOG.md.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[Sweetdevil144]

LGTM