Configs: Last round of "final" changes to configs for v6

[JoshuaKGoldberg]

Following #6014, I described the changes in #7110 as the "final v6 changes to configs". That was inaccurate - it was the final changes to configs before trying them out in real-world projects (#6760). Now that we've tried things out, there are a few more changes I think we should make...

Increasing strictness:

• no-explicit-any: It was moved from recommended to strict, but I think we should move it back. Most projects shouldn't be using any.
• strict-boolean-expressions: Switch allowNullableEnum to false by default, per Changes to configurations for 6.0.0 #6014 (comment)
  • (this was originally listed under the following section erroneously - thanks @tylerlaprade for pointing that out!)

Decreasing strictness:

• no-confusing-void-expressions: It was added to stylistic-type-checked but I think it's too opinionated for many users, especially for those working in JSX-based frameworks. I think we should remove it from stylistic-type-checked for now.
• no-mixed-enums: It was added to recommended, but I think it's a rare enough edge case that a large percentage of consumers wouldn't care for the rule. I think we should instead move it to strict for now. (this is in strict-type-checked, I was wrong)
• sort-type-constituents: It was added to stylistic. It's pretty nitpicky without actual bug-catching and I think many users would be by it. I think we should remove it from stylistic for now.

...anything else that's come up & we should adjust for?

[JoshuaKGoldberg]

Coming over from #7138:

• prefer-string-starts-ends-with: Perhaps Enhancement: [prefer-string-starts-ends-with] Option to ignore [0] === cases? #7140 should be in there?
• Confirmed on no-confusing-void-expressions: we don't like it in stylistic-type-checked. Maybe strict-type-checked, or nothing at all?

[tylerlaprade]

Technically the strict-boolean-expressions: allowNullableEnum change should be listed under the "Increasing strictness" section. Thanks for including it, by the way!

[JoshuaKGoldberg]

Whoops, thanks! Edited :)