…mentations and handle global optimizations (HeahDude)This PR was merged into the 5.1-dev branch.Discussion----------[Form] Added an AbstractChoiceLoader to simplify implementations and handle global optimizations| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | yes| Deprecations? | no| Tickets       | ~| License       | MIT| Doc PR        | ~<!--Replace this notice by a short README for your feature/bugfix. This will help peopleunderstand your PR and can be used as a start for the documentation.Additionally (seehttps://symfony.com/roadmap): - Always add tests and ensure they pass. - Never break backward compatibility (seehttps://symfony.com/bc). - Bug fixes must be submitted against the lowest maintained branch where they apply   (lowest branches are regularly merged to upper ones so they get the fixes too.) - Features and deprecations must be submitted against branch master.-->Taking over#33218 (taking over#30983)The `ChoiceLoaderInterface` is not easy to understand/implement, while its goal is simple, lazy load an array of choices.What may seem complicated is the how/what to optimize loading, we need to deal with a `$value` callback (which refers to the `choice_value` option allowing to transform a model choice to a unique string value that can be displayed/submitted).We have now enough implementations in core to justify the need of an abstraction and provide a better DX in the process.Before this PR we needed to implement 3 methods to create a loader: - `loadChoiceList(?callable $value): ChoiceListInterface` - `loadChoicesForValues(array $values, ?callable $value): array` - `loadValuesForChoices(array $choices, ?callable $value): array`and handle optimization, in each.Now we only need to implement: - `loadChoices():  iterable`and optionnally: - `doLoadChoicesForValues(array $values, ?callable $value): array`if more optimization is needed to only load submitted values, (i.e the core intl loader prevents loading values that are the same as choices, and the doctrine one performs a `WHERE id IN ($ids)` query).Commits-------1394df2 [Form] Added an AbstractChoiceLoader to simplify implementations and handle global optimizations

…eahDude)This PR was merged into the 5.1-dev branch.Discussion----------[Form] Added a "choice_filter" option to ChoiceType| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | yes| Deprecations? | yes| Tickets       |Fix#32657| License       | MIT| Doc PR        |symfony/symfony-docs#13223Finally opening this PR for a very old branch, based on both#34550 (merged) and#30994 (merged).~Until#30994 is merged, this PR should better be reviewed by commits. Thanks!~Commits-------ed2c312 [Form] Added a "choice_filter" option to ChoiceType