linux: Implement local time zone support (#14610)

I decided to remove the GPUI APIs since `chrono` already provides this
functionality, and is already been used for this purpose in other parts
of the code (e.g.
[here](https://github.com/zed-industries/zed/blob/80402a684066628793695d9303979ad993803740/crates/zed/src/main.rs#L756)
or
[here](https://github.com/zed-industries/zed/blob/80402a684066628793695d9303979ad993803740/crates/ui/src/utils/format_distance.rs#L258))

These usages end up calling the `time_format` crate, which takes in a
`UtcOffset`. It's probably cleaner to rewrite the crate to take in
`chrono` types, but that would require rewriting most of the code there.

Release Notes:

- linux: Use local time zone in chat and Git blame