Make AssertEntry and AssertClause interfaces

[andrewbranch]

Fixes #56477

[typescript-bot]

Looks like you're introducing a change to the public API surface area. If this includes breaking changes, please document them on our wiki's API Breaking Changes page.

Also, please make sure @DanielRosenwasser and @RyanCavanaugh are aware of the changes, just as a heads up.

[fatcerberus]

Ugh. I get that this is to fix a real-world break, but interface Foo extends Bar {} is just… yuck.

[andrewbranch]

Getting in the weeds with DefinitelyTyped has conditioned me to see interface Foo extends SomeInterface {} as beautiful and type Foo = SomeInterface as unsettling

[DanielRosenwasser]

TIHI

[andrewbranch]

🤔