Rewrite runtime code loading to fix some problems #8847

Job	Run time
ormolu	9s
build ucm (ubuntu-20.04)	18s
build ucm (macOS-12)	17s
build ucm (windows-2019)	23s
generate jit source	7s
run transcripts (ubuntu-20.04)	9s
run interpreter tests (ubuntu-20.04)	8s
run transcripts (macOS-12)	13s
run interpreter tests (macOS-12)	12s
run transcripts (windows-2019)	33s
build jit binary / build jit binary (ubuntu-20.04)	1m 40s
build jit binary / build jit binary (macOS-12)	5m 17s
build jit binary / build jit binary (windows-2019)	3m 56s
test jit / test jit (ubuntu-20.04)	1m 33s
test jit / test jit (macOS-12)	2m 13s
	17m 8s

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