fix: remove stream editor email duplication

[meadmaker]

These changes will prevent the stream editor email address from being included in the Notice emails field during the creation of a conflict review. This only works for documents in the IRTF or ISE streams.

• If the stream editor email address is detected in the input, then the address is silently removed.
• The address is removed even if it has been entered multiple times.
• The email address suggestion generator has been updated to remove the stream editors
• The help text for the Notice emails field has been updated to say that the stream editors are automatically notified.

While I was in the code, I refactored a bit:

• The SimpleStartReviewForm is now a superclass to the StartReviewForm. This was intended to ease the creation of a single clean_notify() validation method, which eventually moved to the view code instead. However, the refactoring was left.
• The start_review_as_secretariat() and start_review_as_stream_owner() methods are now merged. Ironically, this resulted in the exact same number of lines of code, but at least there is only one method to update going forward.

Fixes ietf-tools/datatracker#3638.

[codecov[bot]]

Codecov Report

Merging #4451 (d840b57) into main (d3f25a6) will decrease coverage by 0.00%. The diff coverage is 96.07%.

@@            Coverage Diff             @@
##             main    #4451      +/-   ##
==========================================
- Coverage   88.43%   88.42%   -0.01%     
==========================================
  Files         296      296              
  Lines       39674    39690      +16     
==========================================
+ Hits        35086    35097      +11     
- Misses       4588     4593       +5     

Impacted Files	Coverage Δ
ietf/doc/views_conflict_review.py	96.51% <95.55%> (-0.24%)	:arrow_down:
ietf/group/forms.py	91.41% <100.00%> (+0.16%)	:arrow_up:
ietf/utils/fields.py	91.57% <100.00%> (+0.04%)	:arrow_up:
ietf/utils/pipe.py	82.60% <0.00%> (-4.35%)	:arrow_down:
ietf/utils/text.py	85.97% <0.00%> (-1.22%)	:arrow_down:
ietf/utils/draft.py	71.39% <0.00%> (-0.21%)	:arrow_down:
ietf/doc/views_search.py	89.44% <0.00%> (+0.20%)	:arrow_up:

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