Adding `proxy` keyword to configure proxy while using zed. After setting
the proxy, restart Zed to acctually use the proxy.
Example setting:
```rust
"proxy" = "socks5://localhost:10808"
"proxy" = "http://127.0.0.1:10809"
```
Closes#9424, closes#9422, closes#8650, closes#5032, closes#6701,
closes#11890
Release Notes:
- Added settings to configure proxy in Zed
---------
Co-authored-by: Jason Lee <huacnlee@gmail.com>
1b261608c6