EC2: Ensure all regions have availability zones

[bblommers]

Related to #8087

Zones are now automatically created for every region that botocore returns - making it future proof for new regions added in the future. Some explicit zone mappings were kept for backwards compatibility.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.49%. Comparing base (ca14870) to head (fb83b3c). Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8125 +/- ## ======================================= Coverage 94.48% 94.49% ======================================= Files 1150 1150 Lines 99011 99021 +10 ======================================= + Hits 93555 93567 +12 + Misses 5456 5454 -2 ``` | [Flag](https://app.codecov.io/gh/getmoto/moto/pull/8125/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto) | Coverage Δ | | |---|---|---| | [servertests](https://app.codecov.io/gh/getmoto/moto/pull/8125/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto) | `28.81% <100.00%> (+<0.01%)` | :arrow_up: | | [unittests](https://app.codecov.io/gh/getmoto/moto/pull/8125/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto) | `94.46% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto#carryforward-flags-in-the-pull-request-comment) to find out more.

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[github-actions[bot]]

This is now part of moto >= 5.0.15.dev16