tpm2: Add RSADecryptWithSession

[thomasten]

I need to use RSADecrypt with a PCR policy. I added RSADecryptWithSession similar to the already existing ...WithSession funcs.

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[3u13r]

We'd like to move away from our fork and back to mainline. Could someone take a look in the near future @jkl73 @alexmwu ?

[alexmwu]

This LGTM.

FYI @chrisfenner is working on a refactor of the API, which you may be interested in. https://github.com/google/go-tpm/tree/tpmdirect. We have 1:1 parameter mapping and support for most commands (with an easy route to adding new commands). We are planning a stable release at that point. As part of the tpmdirect work, we plan on deprecating the current tpm2 package.

@chrisfenner are we planning on accepting new contributions to the legacy package?

[daniel-weisse]

Can this be rebased to main and merged?