devops: Align Filesystem Hierarchy across CI, Docker and Rust code

[gustavovalverde]

Describe the issue or request

Some documentation and Rust code, among other examples, uses /zebrad-cache as the path to save the cache state. We once decided to use the linux Filesystem Hierarchy Standard (FHS) for Docker, and changed some existing paths, including the one for cache state to /var/cache/zebrad-cache, this creates inconsistency and confusion for users and developers.

Expected Behavior

Have the same convention across the whole project, including documentation.

Current Behavior

Paths differ across the project

Possible Solution

Use the Filesystem Hierarchy Standard (FHS) for all paths

Additional Information/Context

I recall some paths were not possible to change (or at least not a good idea), as those were for matching zcashd

An user reported their cache state destroyed, based on this confusion: https://discord.com/channels/809218587167293450/809251029673312267/1150191217032826980

Is this happening on PRs?

N/A

Is this happening on the main branch?

N/A