Deprecate ram/vram configs for smoother migration path to dynamic limits

[RyanJDick]

Summary

Changes:

• Deprecate ram and vram configs. If these are set in invokeai.yaml, they will be ignored.
• Create new max_cache_ram_gb and max_cache_vram_gb configs with the same definitions as the old configs.

The main motivation of this change is to make the migration path smoother for users who had previously added ram /vram to their config files. Now, these users will be automatically migrated into the new dynamic limit behavior (which is better in most cases). These users will have to manually re-add max_cache_ram_gb and max_cache_vram_gb to their configs if they wish to go back to specifying manual limits.

Related Issues / Discussions

See the release notes for RC v5.6.0rc1 for the old migration behavior that we are trying to improve: https://github.com/invoke-ai/InvokeAI/releases/tag/v5.6.0rc1

QA Instructions

• Test that if ram or vram are present in a user's invokeai.yaml, these values are ignored.
• Test that max_cache_ram_gb and max_cache_vram_gb are applied, if set.

Merge Plan

• Don't forget to update the RC release notes accordingly.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)