tpm2sh 0.12.3

[Jarkko Sakkinen <jarkko@kernel.org>]

tpm2sh 0.12.3 loads and processes multi-level ancestor chains correctly,
policy expressions have now a more stable custom-built implemented
parser:

https://crates.io/crates/tpm2sh

The functionality is still mostly focused on key management and TPMKey
ASN.1 generation from various internal and external sources, making
it a tool with kernel testing focus.

I've added optional parentPubkey field to the original TPMKey ASN.1
because that allows "tpm2sh load" to be ergonomic as it can traverse
persistent and cached keys and discover parent, instead of requiring
explicit '--parent' argument.

This transcript demonstrates well the added ergonomics:

~ main ≡
❯ tpm2sh create-primary ecc-nist-p256:sha256
vtpm:80000000

~ main ≡
❯ set DIGEST (tpm2sh policy --mode software 'pcr(sha256:7) or pcr(sha256:15)')

~ main ≡
❯ tpm2sh create -P vtpm:80000000 --data deadbeef --policy $DIGEST keyedhash:sha256 | tpm2sh load
vtpm:80000001

~ main ≡
❯ tpm2sh policy --mode session 'pcr(sha256:7) or pcr(sha256:15)'
vtpm:03000000

~ main ≡
❯ tpm2sh unseal -A vtpm:03000000 vtpm:80000001
deadbeef

~ main ≡
❯ openssl genrsa -out private.pem 2048

~ main ≡
❯ tpm2sh convert -P vtpm:80000000 -I private.pem | tpm2sh load
vtpm:80000002

Without the extra field, also load commands would need to have 
"-P vtpm:80000000".

BR, Jarkko