ek, ak abstractions: allow to specficy exact key type #706

Job	Run time
Check formatting	5s
Check spelling	12s
Check Clippy lints	3m 53s
Check documentation	2m 44s
Check minimum supported rust version (MSRV)	5m 45s
Fedora tests	3m 13s
Fedora rawhide tests	2m 9s
Ubuntu tests	9m 31s
Ubuntu tests on v3.x.y of tpm2-tss	4m 47s
Valgrind test run	7m 38s
	39m 57s

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