Update bundled MySQL version to 8.0.40

[dbussink]

We haven't updated the bundled MySQL version in a while and it also blocks us from upgrading our base Debian version for the containers we build as well.

So update to the latest 8.0.x version here. It's also at least version 8.0.35, which means that updates after this one are going to be much easier as upgrades / downgrades between different patch versions are possible for 8.0.35 and later.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.69%. Comparing base (5468f5d) to head (220dcfd).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17552      +/-   ##
==========================================
- Coverage   67.70%   67.69%   -0.02%     
==========================================
  Files        1584     1584              
  Lines      254718   254718              
==========================================
- Hits       172463   172431      -32     
- Misses      82255    82287      +32     

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[GrahamCampbell]

I've created planetscale/vitess-operator#653 which applies upgrades to the operator. Feel free to throw it away if you had other plans. ;)

[mattlord]

We should also update this:
examples/operator/101_initial_cluster.yaml: mysql80Compatible: mysql:8.0.30

@frouioui are you already coordinating with @dbussink on this? As you both know, it will span many PRs across several repos 🙂 Let me know if you could use any help.

[mattlord]

This shouldn't be v16 should it? Same thing below.

I think that we can remove this section entirely since we do not have 5.7 images in v21 or v22.