Reduce safe integer range to exclude +/- 2^53 and match JavaScript safe-integer bounds

[johnbartholomew]

As noted in #1217 (comment) and discussed in #1238.

Although 2^53 is representable (there is a bit-pattern for a IEEE-754 double precision float which represents this value), it is not safe because as @CertainLach pointed out, it is ambiguous/not distinguishable from 2^53+1 which is not representable and would be rounded down.

This also switches from a StaticError to a RuntimeError when encounting a non-integer-safe value since these values are runtime constructs not parse time (static).

@CertainLach if you have time to review, I'd appreciate it.

Fixes #1238.

[CertainLach]

LGTM (I misunderstood the test twice initially)

[johnbartholomew]

LGTM (I misunderstood the test twice initially)

That sounds like the tests need some more work. I'll see if I can improve it before merging.

[He-Pin]

refs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger#description

[johnbartholomew]

That sounds like the tests need some more work. I'll see if I can improve it before merging.

In an event that probably does not surprise anyone, I did not get time to do this so I'm going to merge now, and then work on further improvements 🫤