Add a shared Bootstrap component resolver

[malberts]

For #70

First step towards loading a single Bootstrap per skin. The four component init scripts
(carousel, modal, popover, tooltip) reached Bootstrap only through the window.bootstrap
global, which ties them to Extension:Bootstrap's copy. They now obtain the component class
from a shared package module: getComponentClass() resolves it from the window.bootstrap
global that Extension:Bootstrap and most Bootstrap-bundling skins expose, or from the jQuery
plugin bridge that skins such as Tweeki register instead (a Bootstrap jQuery plugin's
Constructor is the native component class). The five modules involved are ResourceLoader
package modules, so the resolver is shared via require() rather than a page-wide global.

No loading change: the shared module depends on ext.bootstrap.scripts and the fix modules
depend on the shared module, so the load graph and behaviour are identical to before on
every skin. The jQuery path becomes load-bearing once a later change stops loading
Extension:Bootstrap's copy on skins that bundle their own.

Verification

Automated browser testing (Playwright) on Vector, Chameleon, Medik and Tweeki: on a page
exercising carousel, modal, popover and tooltip, all involved modules reach ResourceLoader
state ready and every component element carries a live Bootstrap instance, with no console
errors from this change. On Tweeki the jQuery-bridge fallback was additionally confirmed
viable (the $.fn plugin Constructors of its bundled Bootstrap are present). CI PHPUnit
(MW 1.43 through master) is green.

_{AI-authored, Claude Code (Fable 5, with Opus 4.8 subagents for implementation and review); design agreed with @malberts in session; diff not human-reviewed; verified with automated browser testing (Playwright) across the four skins above plus CI PHPUnit.}