[11.x] Add \DateTimeInterface and \DateInterval to type for Cache::flexible()

[bram-pkg]

The \Illuminate\Cache\Repository::flexible also supports being passed the following I believe:

cache()->flexible(
  'key',
  [now()->addHour(), now()->addHours(2)],
  fn () => 'value',
);

This is now reflected in the phpdoc. The purpose of this PR is to add these types to be allowed in the docblock, improving PHPStan understanding of the code.

I have used the same ordering of types as on \Illuminate\Cache\Repository::putMany.

This PR will also eliminate the following PHPStan error:

Parameter $ttl of method Illuminate\Cache\Repository::flexible() expects array{int, int}, array{Illuminate\Support\Carbon, Illuminate\Support\Carbon} given.

[crynobone]

Marking as draft since tests are failing

[bram-pkg]

I'm not sure the tests are actually failing, it seems the CI is just having a fit:

[bram-pkg]

I do not have permission to re-run the CI, so you'll have to do that or I can push an empty commit.