chore(ci): upgrade GHA runner image to Ubuntu 26.04

[hainenber]

chore(ci): upgrade GHA runner image to Ubuntu 26.04

SUMMARY

Very much self-titled. Ubuntu 26.04 trims off quite a lot of installations so in theory, this should help with job init time

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TESTING INSTRUCTIONS

Green CI as acceptance criterion

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[bito-code-review]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.15%. Comparing base (bda62cb) to head (aaad939).
⚠️ Report is 27 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #42191      +/-   ##
==========================================
+ Coverage   65.08%   65.15%   +0.07%     
==========================================
  Files        2758     2768      +10     
  Lines      155229   156065     +836     
  Branches    35572    35719     +147     
==========================================
+ Hits       101026   101691     +665     
- Misses      52288    52411     +123     
- Partials     1915     1963      +48     

Flag	Coverage Δ
hive	38.61% <ø> (-0.33%)	⬇️
javascript	70.77% <ø> (ø)
mysql	57.86% <ø> (+0.23%)	⬆️
postgres	57.92% <ø> (+0.23%)	⬆️
presto	40.55% <ø> (-0.35%)	⬇️
python	59.32% <ø> (+0.22%)	⬆️
sqlite	57.54% <ø> (+0.24%)	⬆️
unit	100.00% <ø> (ø)

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[rusackas]

Nice cleanup and CI's green, but check-python-deps.yml, the python-dependency-liccheck job, and both playwright-tests / playwright-tests-experimental are still on ubuntu-22.04 while everything else jumped to 26.04. Is that intentional (like the flaky-on-24.04 comment on cypress-matrix) or just missed? Leaving the two heaviest test jobs on the old image seems to undercut the job-init speedup this PR is going for.

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