Tweaks for renting buffer from the array pool in INumberBase

[gfoidl]

Basically it's

-if (textMaxCharCount < 256)
+if (textMaxCharCount <= 256)

to use stack-alloc when the count is the same as the stack threshold, and

-utf16Text = utf16TextArray.AsSpan(0, textMaxCharCount);
+utf16Text = utf16TextArray;

to avoid the slicing as the buffer in the to be called methods can be larger than needed thus to avoid some unnecessary work.

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[tannergooding]

LGTM.

Just noting that this code doesn't really matter, it's a fallback to ensure that we don't get a method not found exception and should never be called for typical user-types.

That is, anyone implementing an interface should typically be providing their own implementation and ignoring the DIM's existence, especially if performance is a consideration.