Rework SolutionLoader #9083

Job	Run time
lint/style-and-typos	1m 34s
linux/3.10/bare-env	0s
${{ matrix.TARGET }}/${{ matrix.python }}${{ matrix.other }}	0s
process-coverage-linux	24s
process-coverage-osx	26s
process-coverage-win	47s
	3m 11s

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