ENH: Scaffold GridFieldFilterHeader filters for ArrayList based GridFields.

[mfendeksilverstripe]

Description

Enables filtering capability for cases where GirdField data is stored in an ArrayList. This wasn't working before because pre CMS 5 such feature was not supported. With CMS 5 it's possible so we should enable it.

Issues

• GridFieldFilterHeader and ArrayLists #10654
• Localisation manager > Filter capability tractorcow-farm/silverstripe-fluent#924

Likely replaces tractorcow-farm/silverstripe-fluent#922

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[GuySartorelli]

Haven't tested yet, but a few (mostly minor) things stood out in a quick review

[GuySartorelli]

Suggested change

	if ($list instanceof ArrayList) {
	if (!($list instanceof DataList)) {

Allows for other list implementations that don't use the database (e.g. EagerLoadedList but also project-specific implementations people may make)

[GuySartorelli]

There is a failed unit test that seems relevant - can you please take a look?

1) SilverStripe\Forms\Tests\GridField\GridFieldFilterHeaderTest::testGetBasicSearchContext
We expect the search filters to be different as the filtering is different based on how data is provided to the GridField
Failed asserting that two arrays are not identical.

/home/runner/work/silverstripe-framework/silverstripe-framework/tests/php/Forms/GridField/GridFieldFilterHeaderTest.php:339
/home/runner/work/silverstripe-framework/silverstripe-framework/vendor/bin/phpunit:122