ref(mediators): Convert AlertRuleActionRequester to dataclass

[Christinarlong]

Convert the AlertRuleActionRequester mediator to a dataclass and update refs to point to this new class. Also moves the utils for external_requests while were at it.

Would also appreciate any suggestions for how to name the directories/structure

issue ref (#73857 )

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 94.11765% with 2 lines in your changes missing coverage. Please review.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...s/external_requests/alert_rule_action_requester.py	92.59%	1 Missing and 1 partial :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #78559       +/-   ##
===========================================
+ Coverage   56.64%   78.14%   +21.49%     
===========================================
  Files        7065     7090       +25     
  Lines      311512   312663     +1151     
  Branches    50895    51092      +197     
===========================================
+ Hits       176470   244318    +67848     
+ Misses     130519    61964    -68555     
- Partials     4523     6381     +1858