Consolidate Build & Test CI #21

Job	Run time
Build Element Web	1m 23s
Prepare Element Desktop	0s
Downstream Playwright tests [element-modules]	0s
end-to-end-tests	33s
Desktop Windows	0s
Run Tests [${{ matrix.project }}] ${{ matrix.runner }}/${{ needs.build_ew.outputs.num-runners }}	1s
Desktop Linux	0s
Desktop macOS	0s
	1m 57s

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