Client::block_for_drive too expensive to reasonably use

[jojo2357]

Client::block_for_drive was too expensive to use in missioncenter, instead I build my own cache so i can lookup block devices for a drive.

The code iterates thru every block, which i call for every drive which has a very bad runtime, roughly d^2 when using a cache reduces it to d.

[FineFindus]

Mirror of my earlier comment, for context:
Most of the time is probably spent at awaiting through the blocks sequentially, rather than awaiting all blocks at once. This was done as the most straightforward port of the C version, making it easier to port/check for correctness.

It's on my TODO list to be refactored, along with the other similar functions, but I'm waiting for async-closures to be stabilized in rust-2024, as I hope it will make the code much easier to read/write/maintain.