feat: implement shadowing rules #4134

Job	Run time
build (1.21.x, GOARCH=amd64 GOOS=linux, gno)	10s
test (1.21.x, _test.cmd)	57s
build (1.21.x, GOARCH=wasm GOOS=js, gno)	25s
test (1.21.x, _test.pkg)	29s
build (1.22.x, GOARCH=amd64 GOOS=linux, gno)	9s
test (1.21.x, _test.gnolang.native)	22s
build (1.22.x, GOARCH=wasm GOOS=js, gno)	26s
test (1.21.x, _test.gnolang.stdlibs)	55s
test (1.21.x, _test.gnolang.realm)	34s
test (1.21.x, _test.gnolang.pkg0)	1m 25s
test (1.21.x, _test.gnolang.pkg1)	5m 57s
test (1.21.x, _test.gnolang.pkg2)	3m 52s
test (1.21.x, _test.gnolang.other)	18s
test (1.22.x, _test.cmd)	53s
test (1.22.x, _test.pkg)	28s
test (1.22.x, _test.gnolang.native)	21s
test (1.22.x, _test.gnolang.stdlibs)	54s
test (1.22.x, _test.gnolang.realm)	24s
test (1.22.x, _test.gnolang.pkg0)	1m 27s
test (1.22.x, _test.gnolang.pkg1)	6m 0s
test (1.22.x, _test.gnolang.pkg2)	3m 47s
test (1.22.x, _test.gnolang.other)	24s
upload-coverage	11s
	30m 48s

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