feat: make tests run in parallel #2379

Job	Run time
build (1.20.x, GOARCH=amd64 GOOS=linux, gno)	20s
build (1.20.x, GOARCH=wasm GOOS=js, gno)	34s
build (1.21.x, GOARCH=amd64 GOOS=linux, gno)	20s
build (1.21.x, GOARCH=wasm GOOS=js, gno)	26s
test (1.20.x, _test.cmd)	1m 6s
test (1.20.x, _test.pkg)	51s
test (1.20.x, _test.gnolang.native)	53s
test (1.20.x, _test.gnolang.stdlibs)	1m 17s
test (1.20.x, _test.gnolang.realm)	54s
test (1.20.x, _test.gnolang.pkg0)	1m 38s
test (1.20.x, _test.gnolang.pkg1)	6m 27s
test (1.20.x, _test.gnolang.pkg2)	4m 37s
test (1.20.x, _test.gnolang.other)	46s
test (1.21.x, _test.cmd)	1m 49s
test (1.21.x, _test.pkg)	1m 2s
test (1.21.x, _test.gnolang.native)	45s
test (1.21.x, _test.gnolang.stdlibs)	1m 0s
test (1.21.x, _test.gnolang.realm)	37s
test (1.21.x, _test.gnolang.pkg0)	2m 9s
test (1.21.x, _test.gnolang.pkg1)	6m 7s
test (1.21.x, _test.gnolang.pkg2)	4m 3s
test (1.21.x, _test.gnolang.other)	26s
upload-coverage	12s
	38m 19s

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