fix(decoder): Correctly unmarshal !!int tagged values #702

Job	Run time
lint	13s
Fuzzing Test	1m 20s
Test in i386 (ubuntu-latest, 1.23)	18s
Test in i386 (ubuntu-latest, 1.21)	18s
ycat	11s
Test in i386 (windows-latest, 1.22)	1m 56s
Test in i386 (windows-latest, 1.23)	2m 12s
Test in i386 (ubuntu-latest, 1.22)	18s
Test in i386 (windows-latest, 1.24)	2m 18s
Test with -race (ubuntu-latest, 1.23)	11s
Test with -race (ubuntu-latest, 1.21)	29s
Test in i386 (ubuntu-latest, 1.24)	23s
Test with -race (macos-latest, 1.21)	28s
Test with -race (ubuntu-latest, 1.22)	29s
Test with -race (macos-latest, 1.22)	25s
Test in i386 (windows-latest, 1.21)	1m 23s
Test with -race (macos-latest, 1.23)	21s
Test with -race (windows-latest, 1.21)	2m 31s
Test with -race (ubuntu-latest, 1.24)	25s
Coverage	19s
Test with -race (windows-latest, 1.22)	1m 25s
Test with -race (windows-latest, 1.24)	1m 38s
page	43s
Test with -race (windows-latest, 1.23)	49s
Test with -race (macos-latest, 1.24)	26s
	21m 29s

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