chore(site-db-user): remove instances of old db user manager

[tanmoysrt]

• added archive_site_database_users function to call on site archive or moving to some unsupported site plan

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 39.68%. Comparing base (6b2f07f) to head (4d97a3f).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
press/press/doctype/site/site.py	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2305      +/-   ##
==========================================
+ Coverage   39.65%   39.68%   +0.02%     
==========================================
  Files         375      375              
  Lines       28610    28537      -73     
==========================================
- Hits        11345    11324      -21     
+ Misses      17265    17213      -52     

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