Support TPM2_StirRandom

The `tpm2` package implements `TPM2_GetRandom` but not its counterpart `TPM2_StirRandom` (Part 3, section 16.2), so there is no way to contribute entropy to the TPM's RNG state through this package, yet.

Start in the tpm2 package by tracing the existing TPM2_GetRandom implementation and compare its command structure with TPM2_StirRandom in Part 3, section 16.2. Add the missing package support for contributing entropy and verify it with the repository's relevant tests or TPM command checks.

Written by the indexing model from the issue text.