feature: switch to personal-files interface as a less intrusive location for models

[frenchwr]

The primary change here is to switch from installing stable diffusion models at ~/openvino-ai-plugins-gimp to a hidden directory at ~/.local/share/openvino-ai-plugins-gimp. This requires adding the personal-files interface to the new snap (which will likely trigger a manual review of the gimp snap as it did for the openvino-ai-plugins-gimp snap). See this forum post for more discussion.

Other changes:

• Remove manual interface connections for openvino-ai-plugins-gimp snap as those now autoconnect 🥳
• Switch to main branch for fetching command-chain script

[frenchwr]

The build is failing because of the new interface:

Errors
------
 - declaration-snap-v2:plugs_installation:dot-local-share-openvino-ai-plugins-gimp:personal-files
	human review required due to 'allow-installation' constraint (bool)
gimp_2.99.16_amd64.snap: FAIL

I will reach out to the store team to request a review and then we can re-run.

[jnsgruk]

Hey, you can update the declarations to unblock the build like this: https://github.com/snapcrafters/gimp/blob/candidate/.github/slot-declaration.json

[frenchwr]

Hey, you can update the declarations to unblock the build like this: https://github.com/snapcrafters/gimp/blob/candidate/.github/slot-declaration.json

Added a plot-declaration.json and that fixed the build - thanks!

[jnsgruk]

One minor change, then we're good to merge. Thanks!