Review tsconfigs with ts 5 multi-extension

[luxaritas]

Since TS 5 supports extending from multiple base configurations, we should check if any of our config setup would benefit from taking advantage of this. I can't remember if I had a use case for this when setting this up or if it was ultimately irrelevant (ie just issues around lack of type field merging, config-relative path definition, etc or only relevant for having a base tsconfig to define paths, which we're not using)