Improve folding logic for tags-based modes

[mkslanc]

Issue #, if available: #5985

Description of changes:
Now it uses open tag start row to determine starting column on getFoldWidgetRange

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts

Open kitchen-sink @ e7339299b7732054fd41fb694e02dcb669736d5d

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.71%. Comparing base (f82010e) to head (e733929).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5987      +/-   ##
==========================================
- Coverage   93.73%   93.71%   -0.03%     
==========================================
  Files         641      641              
  Lines      138167   138193      +26     
  Branches    14561    14535      -26     
==========================================
- Hits       129510   129501       -9     
- Misses       8657     8692      +35     

Flag	Coverage Δ
unittests	93.71% <100.00%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.