Add "Default Tip" and "Default Warning" settings to custom fields

[mmikkel]

...I'm loving the "Tip" and "Warning" field instance settings introduced to entry types in Craft 5.4, and use them all the time!

However, the fact that – unlike w/ Instructions – it isn't possible to set a default Tip and/or Warning for custom fields, feels like an oversight and is a limitation that is a little bit frustrating at times.

To that end, it'd be awesome if custom fields could have new "Default Tip" and "Default Warning" settings, similar to the "Default Instructions" setting.

[mmikkel]

...I still miss having "Default Tip" and "Default Warning", on every build 😢 Would be a great and much appreciated little addition to 5.9!