Keep WordUtils.wrap from splitting a surrogate pair

[alhudz]

Port of apache/commons-lang#1731 to the Commons Text copy of WordUtils, as requested by @garydgregory.

WordUtils.wrap(str, wrapLength, newLineStr, true) hard-breaks a too-long word at the fixed char offset wrapLength + offset and inserts the new line there. When that offset lands between the high and low surrogate of a supplementary code point the pair is split, so a lossless wrap emits a lone high surrogate at the end of one line and a lone low surrogate at the start of the next.

Repro: WordUtils.wrap("a😀😀😀😀", 4, "\n", true) (a then four U+1F600).
Before: a😀\uD83D \n \uDE00😀\uD83D \n \uDE00, i.e. the 2nd and 4th emoji are split around the \n.
After: a😀😀\n😀😀, no lone surrogates.

Fix: nudge the break one char forward when it would land inside a pair, so the whole code point stays on the current line. BMP input and the delimiter-based wrap paths are unaffected, and the other wrap overloads delegate to this method.

Added assertions to WordUtilsTest#testWrap_StringIntStringBoolean that fail on the current tree and pass with the fix.

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[garydgregory]

Thank you @alhudz , merged 🚀