New core functions: toDate and toDateTime

[jamisonbryant]

Adds two new global functions: toDate() and toDateTime() which accept mixed values and attempt to convert them to the native Chronos object. This is the first part of a series of PRs to make type-safe request data available to users.

[jamisonbryant]

I just realized also that some tests are failing on PHP8.4 specifically that are passing on 8.3 and below:

DateRangeError: DateTimeImmutable::createFromTimestamp(): Argument #1 ($timestamp) must be a finite 
  number between -9223372036854775808 and 9223372036854775807.999999, NAN given
// (same for -INF)
// (same for INF)

I tried work around this by simply adding |\DateRangeError to the try-catch block but this class is only available in PHP8.3 and up, and composer.json is currently set at >=8.1. So I changed the exception to catch Throwable instead. I've never written try-catch blocks this 'broad' before so if this the wrong approach I would love to get some feedback.

Alternatively, we can remove the tests for NAN/INF and assume users will not try to pass these values to the functions, which I think is semi-reasonable.