A way of overriding Zed config folders

[Igonato]

Check for existing issues

• Completed

Describe the feature

Allow a way of overriding Zed's service dirs. For example, through environment variables:

ZED_CONFIG_DIR=foo/bar zed .

Developer Use Case:

A developer working on Zed can run it with different settings which aren't used by the main editor instance (which can be useful when working on experimental features). No chance of corrupting the main setup. Having separate logs between the instances is useful to avoid confusion.

User Use Case

Allow users run Zed in a portable fashion, storing all configuration files, logs, and other data in their directory of choice (e.g. on a thumb drive). Allow use of Zed in restrictive environments (e.g. can't have executables in AppData)

#13300 is related in a sense that what is asked there can be archived through configuration folder override, but the ergonomics are less than ideal. I think it is good to have both, total settings override and per-project settings tweaks.