der: deprecate `TagNumber::new` #2351

Job	Run time
build (stable, wasm32-unknown-unknown)	50s
build (stable, thumbv7em-none-eabi)	52s
build (1.81.0, wasm32-unknown-unknown)	55s
fuzz	2m 11s
build (1.81.0, thumbv7em-none-eabi)	51s
test (1.81.0)	2m 29s
test (stable)	2m 29s
minimal-versions	0s
	10m 37s

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