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?

[nicholasbishop]

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.

The HII data isn't something I'm very familiar with, so I don't have a strong opinion yet on adding a dep like binrw. I'd suggest as a first step, to try writing some representative code so that we can see what it looks like and put up an example PR. Feel free to use binrw or whatever other deps. Then we can evaluate how best to approach it. For example, we could decide to add it as an optional dep, so that it's only used when a hii feature is enabled, or even put hii parsing in an entirely separate package from uefi.

[nicholasbishop]

Lgtm. I rebased to fix the changelog conflict.