Add (partial) safe protocol implementation for EFI_HII_DATABASE_PROTOCOL

[seijikun]

This only grants access to the HII-database's raw buffer for now.

Checklist

• Sensible git history (for example, squash "typo" or "fix" commits). See the Rewriting History guide for help.
• Update the changelog (if necessary)

[seijikun]

This is one of the last things we (IP-Projects) need ... for now.
Our end goal with this protocol is to be able to read the collection of available BIOS settings (+ their values), which requires to fully parse the hiidb datastructure.

Though I'm somewhat at a loss as to how to continue with this.
I think parsing hiidb without the help of some library is a big no-no, since this is what it looks like with a helping library.

Would it be acceptable to add a new dependency on something like binrw to add this to uefi-rs, or do you regard hiidb parsing as out-of-scope for uefi-rs alltogether?

[phip1611]

Would it be acceptable to add a new dependency on something like binrw to add this to uefi-rs, or do you regard hiidb parsing as out-of-scope for uefi-rs alltogether?

Not sure, we haven't done this so far. I have a light tendency towards no. In the documentation of the corresponding "high level" abstraction in uefi (pub struct HiiDatabase(HiiDatabaseProtocol);, you could add some more context for higher-level usages?