cleanup rust code

[cyberpunks]

There are low-hanging fruit for silencing clippy lints, removing unnecessary allocations, and writing a more efficient version of .retain().

[cyberpunks]

Branch rust-cleanup1 at ​​​​​https://gitgud.io/onionk/tor.git

[cyberpunks]

Reviewing this should wait until a rebase after other Rust code changes like #27197 and #27206 are merged, since there are conflicts.

[chelseakomlo]

Thanks for the patch. Looking over the commits on this branch, it looks like there are a lot of small changes and several refactoring commits (For example,renaming functions, etc). Can you please separate this ticket into more specific tickets/patches? For example, I recommend creating a ticket for Clippy fixups, a separate ticket for creating a more efficient .retain(), etc. This will help us more effectively and quickly review these changes.

To organize these, feel free to keep this issue as the parent ticket with sub-tickets for each change.

[cyberpunks]

Replying to chelseakomlo:

a separate ticket for creating a more efficient .retain(),

That one's #27206, which nobody has reviewed yet still.

[nickm]

Marking a number of 0.3.5 tickets as possible, maybe even a good idea, for later. Possibly backportable, some of them. But not currently things to do as part of 0.3.5 stabilization.