refactor: change alert parts calculations

[AleksandrMatsko]

Change the rule for calculating alert parts if they are too big

There is no limits on tag length and tags count, so users can use a lot of long tags. In such case the function that resizes alert parts got bad data, which results to wrong calculations and panic in notifier.

This PR offers new function for resizing alert parts. Now the space is distributed between tags, trigger description and events block. If possible, space is given to description and events.

This PR affects the following senders:

• mattermost
• slack
• telegram

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 85.71429% with 11 lines in your changes missing coverage. Please review.

Project coverage is 52.64%. Comparing base (0197720) to head (3493326).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
senders/calc_message_parts.go	82.75%	4 Missing and 1 partial ⚠️
senders/msgformat/highlighter.go	70.00%	2 Missing and 1 partial ⚠️
senders/telegram/message_formatter.go	85.71%	2 Missing and 1 partial ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1084       +/-   ##
===========================================
- Coverage   66.85%   52.64%   -14.21%     
===========================================
  Files         219      287       +68     
  Lines       12778    16593     +3815     
===========================================
+ Hits         8543     8736      +193     
- Misses       3684     7303     +3619     
- Partials      551      554        +3     

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[github-actions]

Build and push Docker images with tag: 2024-10-23.ae27338