Restore loading of vector-fix CSS modules

[malberts]

Two commits, two concerns. Fixes #84.

1. Restore loading of vector-fix CSS modules — af96510

The replacement sparse-loading foreach added in #80 (HooksHandler::onParserAfterParse) called getModulesFor( $activeComponent ) without a skin argument, returning only the default module group. The Vector-fix modules live in the vector group and were therefore silently dropped on every skin. Adding back 'vector' reinstates the per-skin group that AbstractComponent::augmentParserOutput() had been passing since 5.2.0 (commit f5a9c9f) — the path that MW 1.43's ParserOutputAccess lifecycle change silently disabled, which is precisely what #80 set out to compensate for via the post-parse hook.

2. Drop heavy mock-based test for the post-parse module loader — c0ac01b

Per Jeroen's review on #80, the test that landed alongside the sparse-loading patch pinned a single argument literal through deep mocks of every collaborator on HooksHandler, coupling to call signatures rather than behaviour. Integration verification on the running rig is the more reliable signal for this regression.

[malberts]

For the record on the "previous behaviour" framing in the commit
message: the 5.2.x line has loaded modal.vector-fix /
popover.vector-fix for every skin (not just Vector-family ones)
since f5a9c9f ("did some refactoring", 2024-07-13),
which first shipped in 5.2.0. That commit changed
AbstractComponent::augmentParserOutput()'s call from

$this->getComponentLibrary()->getModulesFor(
    $this->getComponentName(),
    $this->getParserOutputHelper()->getNameOfActiveSkin()
);

to

$this->getComponentLibrary()->getModulesFor(
    $this->getComponentName(),
    'vector'
);

alongside the broader BootstrapComponentsService refactor. So this
PR restores the documented 5.2.x behaviour by routing the same
hard-coded 'vector' through the post-parse hook (the only path
that survives MW 1.43+'s ParserOutputAccess lifecycle change). A
principled redesign — passing the active skin, deciding which
skins actually need the workaround, possibly retiring
top: 60px for non-Vector chromes — belongs in 6.0; this stays
strictly minimal-change for the 5.2.4 patch.

Before 5.2.0 (1.0 through 5.1.2), the second arg was the active
skin name, not a hard-code (see the initial-commit form),
so the per-skin scope was different.

[malberts]

Manually tested with: MW 1.43.8 + Bootstrap extension 5.0.0 [= BS framework 4.6.2] + BC 5.2.3), two BS4 stacks, all six skins.

Skin	Pre-fix (BC 5.2.3 vanilla)	Post-fix (PR applied)
Vector 2022	Backdrop renders above modal; page unselectable	Backdrop suppressed; modal usable
Vector (2011 / legacy)	Same as Vector 2022	Same as Vector 2022
MonoBook	Same	Same
Timeless	Same	Same
Chameleon 5.x	Modal + backdrop render correctly (no bug)	Backdrop suppressed; modal still works
Medik 4.x	Same as Chameleon	Same as Chameleon