re-factor Propel1 ModelChoiceList

* add BaseModelChoiceListTest ensuring compatibility
* fix keys and order are preserved
* fix lazy-load to use filters of initial query
bug #9469 [2.2][Propel1] re-factor Propel1 ModelChoiceList (havvg)

This PR was merged into the 2.2 branch.

Discussion
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[2.2][Propel1] re-factor Propel1 ModelChoiceList

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | fixes propelorm/Propel#789
| License       | MIT

replaces #9458

Commits
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613b5f6 re-factor Propel1 ModelChoiceList