Update stockpiles.lua to add functionality to import/export that was a work in progress before modification.

[unboundlopez]

Added functionality to import export on the stockpile menu.

Fixes: #4999

[unboundlopez]

pre-commit.ci autofix

[unboundlopez]

Dwarf.Fortress.2024.10.13-12.24.mp4

[chdoc]

@myk002 Could you provide some context on 856237c (Part of #3285)

It looks to me like the functionality provided by this PR was already partially implemented, but commented out, beforehand.

[ab9rf]

Please give this PR a more descriptive name than "update stockpiles.lua". We often depend on being able to review code history to understand why code is the way it is, and commits and PRs with nondescript titles and descriptions are not helpful to this end.

[unboundlopez]

Updated the title.

[myk002]

@myk002 Could you provide some context on 856237c (Part of #3285)

It looks to me like the functionality provided by this PR was already partially implemented, but commented out, beforehand.

Yeah, I got scared off from designing a UI that would make generated material filters and property filters intuitive. The stockpiles API is quite intimidating (and I say that even though I'm the one who wrote it). I was also completely burned out on stockpiles after the massive effort that went into updating the stockpiles plugin code so it could act as a backend for quickfort stockpile config scripting: https://docs.dfhack.org/en/stable/docs/guides/quickfort-user-guide.html#stockpile-configuration.

However, a simple approach like what this PR implements would at least be useful for copy/pasting stockpiles within a single fort, which is still a worthy use case.