Final cleanup of set_telescope_pointing

[stscijgbot-jp]

Issue JP-2337 was created on JIRA by Jonathan Eisenhamer:

When the final Technical Report, JWST-STScI-005690, SM-12, is produced, the below is the "wish list" of things to do to cleanup/finalize set_telescope_pointing, presented in no particular order:

• Remove/archive all older/defunct methods. Update documentation and tests accordingly.
• Refactor using astropy.units
• Refactor using astropy.models
• Refactor EngDbDirect.get_values, to make building the return more efficient. Note: unnecessary use of extract_db_time in the loop.
• Enable array return when the pointing reduction function returns multiple pointings.
• When using pysiaf, log the PRD version in effect with pysiaf.JWST_PRD_VERSION
• Use/explain the ICS notation
• Refactor func names for consistency