feat(severity): Create a new "high priority" alert

[snigdhas]

Adds a new alert condition, HIghPriorityIssueCondition, which evaluated to true if:

• an issue is high severity (> 0.1 severity score)
• an archived issue escalatings
• a new issue (< 1 day old) is detected as escalating

Up next - further testing in a personal project, checking the email formatting and reason

Fixes #59872

[codecov]

Codecov Report

Merging #61186 (cc37678) into master (ada0212) will increase coverage by 27.90%.
Report is 1 commits behind head on master.
The diff coverage is 83.33%.

❗ Current head cc37678 differs from pull request most recent head ac8ce3d. Consider uploading reports for the commit ac8ce3d to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #61186       +/-   ##
===========================================
+ Coverage   53.17%   81.08%   +27.90%     
===========================================
  Files        4288     5186      +898     
  Lines      176775   227771    +50996     
  Branches    29747    38219     +8472     
===========================================
+ Hits        93996   184682    +90686     
+ Misses      81608    37465    -44143     
- Partials     1171     5624     +4453     

Files	Coverage Δ
...entry/api/endpoints/project_rules_configuration.py	96.66% <100.00%> (ø)
src/sentry/conf/server.py	89.47% <ø> (-0.28%)	⬇️
src/sentry/features/__init__.py	100.00% <100.00%> (ø)
src/sentry/rules/conditions/high_priority_issue.py	81.25% <81.25%> (ø)

... and 2097 files with indirect coverage changes