Expand docker upgrade test, sunset E2E upgrade test

[dereknola]

Proposed Changes

• The E2E upgrade is too big to run on GHA runners (and thus was run on the old Drone CI runners). With Drone dead, we need to migrate this coverage to another test.
• Move the upgrade testlets to the from the E2E version to the Docker version.
• Increase the number of servers for the docker version from 1 to 3, matching the E2E upgrade cluster test in number of nodes.

Types of Changes

CI improvement

Verification

CI is still green, test passes. Test takes ~4min compared to the previous ~2.5m, but thats still alot better than the E2E upgrade test of ~7 to 10m.

Testing

All Testing

Linked Issues

N/A

User-Facing Change

Further Comments

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 21.41%. Comparing base (c0b1314) to head (c6e48de).
⚠️ Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13338      +/-   ##
==========================================
- Coverage   21.42%   21.41%   -0.01%     
==========================================
  Files         187      187              
  Lines       15296    15296              
==========================================
- Hits         3277     3276       -1     
- Misses      11573    11574       +1     
  Partials      446      446              

Flag	Coverage Δ
unittests	21.41% <ø> (-0.01%)	⬇️

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