perf(Core): Reduce empty array allocations further

[Numpsy]

Similar to #851

Calling Array.collect with an empty array results in the allocation of one zero length single dimensional array and one zero length two dimensional array, and as this function is called with huge frequency, this results in a substantial number of allocations.
The early exit also seems to avoid the allocation of a lambda in the empty case, reducing allocations further.

Benchmarks:

Before:

Method	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
LintParsedFile	845.7 ms	6.99 ms	6.19 ms	20000.0000	7000.0000	1000.0000	325.1 MB

After

Method	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
LintParsedFile	817.4 ms	4.79 ms	4.25 ms	14000.0000	5000.0000	1000.0000	229.87 MB

[Numpsy]

Changes made after I got this from running the benchmark project through the Visual Studio alllocation profiler:

Near 1.4 million instances of WarningDetails[0] totalling ~33 million bytes, and a similar number of instances of WarningDetails[0][], and this would remove a big chunk of those. The allocation savings reported by BDN were more than I expected here as it seems that it might avoid some lambda/closure allocations as well.

The way that Array.collect seems to allocate two zero length arrays when called with a zero length input seems unfortunate to me, to the point where I wonder if it would be worth querying if it would be worth making it exit early to avoid at least one of those for an empty input.

[knocte]

Thanks @Numpsy !