refactor: move crypto/kms APIs to spi module.

[Moopli]

Also includes some cleanup refactoring in component/kmscrypto.

[codecov]

Codecov Report

Merging #3558 (d9f6d8e) into main (6013a6b) will increase coverage by 0.04%.
The diff coverage is 93.93%.

@@            Coverage Diff             @@
##             main    #3558      +/-   ##
==========================================
+ Coverage   87.71%   87.75%   +0.04%     
==========================================
  Files         352      351       -1     
  Lines       48638    48612      -26     
==========================================
- Hits        42662    42659       -3     
+ Misses       4428     4404      -24     
- Partials     1548     1549       +1     

Impacted Files	Coverage Δ
...to/crypto/primitive/bbs12381g2pub/bbs12381g2pub.go	87.09% <ø> (ø)
...ent/kmscrypto/crypto/primitive/bbs12381g2pub/fr.go	100.00% <ø> (ø)
...t/kmscrypto/crypto/primitive/bbs12381g2pub/keys.go	85.60% <ø> (ø)
...ypto/primitive/bbs12381g2pub/proof_of_knowledge.go	98.07% <ø> (ø)
...crypto/crypto/primitive/bbs12381g2pub/signature.go	100.00% <ø> (ø)
...rypto/primitive/bbs12381g2pub/signature_message.go	100.00% <ø> (ø)
.../crypto/primitive/bbs12381g2pub/signature_proof.go	84.04% <ø> (ø)
.../kmscrypto/crypto/primitive/bbs12381g2pub/utils.go	100.00% <ø> (ø)
...nent/kmscrypto/crypto/tinkcrypto/cl_crypto_stub.go	100.00% <ø> (ø)
...mponent/kmscrypto/crypto/tinkcrypto/key_wrapper.go	82.89% <ø> (ø)
... and 67 more

... and 3 files with indirect coverage changes

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[DRK3]

Would be better to rename km2 to something else more descriptive, perhaps spikms (same comment applies to other places in this PR)

[Moopli]

done!

[DRK3]

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