build: Docs ci condition on latest link

[stanbrub]

• Added checkout to symlink and some git setup
• Add git sort of versions to tell latest
• Set latest link always to the latest version, not the current branch version
• Tested this on my fork and local branch on deephaven-core

Related: https://github.com/deephaven/deephaven-core/issues/5591

[stanbrub]

Removed using config/temp-tag and now use standard sort version instead. Tests show that this behaves like git's sort version mechanism. So, no git config, no temporary tag, and uses a standard utility that's available in the OS install.

We could turn this into a script if that's better for sharing.

[mattrunyon]

Was testing a filter for looking at docs PRs in core and saw this. The symlinks have been changed and we don't want the version to be latest now (plus this is a year old). Closing.