20231030 2059 pkcs11

[Firstyear]

Fixes #2059 - This allows loading a PKey from a store by uri. I have already tested this as working with a pkcs11 tpm provider.

I have some questions about how to get this to a "mergeable" state.

• Do you have a preferred method for running tests for a feature like this, especially where there are external requirements like pkcs11?
• Is the approach in the handwritten section correct for ffi?
• I'm not sure how you would like the api structured generally in Store - Stores can be re-used so I could make this use new(uri) instead and then have methods for get_private_key / get_public_key. So some advice on how to shape the api would be good.

I think after this the next step will be to allow creating keys with propqueries per https://github.com/latchset/pkcs11-provider/blob/main/tests/tgenkey.c#L141

[Firstyear]

@WolfDan

[Firstyear]

Is it possible to get someone to look at this, as I'd like to be able to contribute this.