Missing tests for nonzero output of localeCompare respecting canonical equivalence

[gibson042]

Followup from #3439:

I'd also like to add some tests verifying that non-zero output [from String.prototype.localeCompare] is not affected by changing between canonically equivalent sequences in a substring, but I'm not sure where to add them. And at any rate, they can be introduced in a followup.

Some examples of what to verify:

• Canonical equivalence between Å [U+212B ANGSTROM SIGN] and Å [U+0041 LATIN CAPITAL LETTER A, U+030A COMBINING RING ABOVE] implies that "\u0426".localeCompare("\u212B") and "\u0426".localeCompare("A\u030A") must have the same sign.
• Canonical equivalence between Å [U+212B ANGSTROM SIGN] and Å [U+0041 LATIN CAPITAL LETTER A, U+030A COMBINING RING ABOVE] implies that "A\u0361".localeCompare("\u212B") and "A\u0361".localeCompare("A\u030A") must have the same sign.
• Canonical equivalence between Ω [U+2126 OHM SIGN] and Ω [U+03A9 GREEK CAPITAL LETTER OMEGA] implies that "\u0426".localeCompare("\u2126") and "\u0426".localeCompare("\u03A9") must have the same sign.
• Canonical equivalence between ṩ [U+1E69 LATIN SMALL LETTER S WITH DOT BELOW AND DOT ABOVE] and ṩ [U+0073 LATIN SMALL LETTER S, U+0307 COMBINING DOT ABOVE, U+0323 COMBINING DOT BELOW] implies that "\u0426".localeCompare("\u1E69") and "\u0426".localeCompare("s\u0307\u0323") must have the same sign.
• Canonical equivalence between ṩ [U+1E69 LATIN SMALL LETTER S WITH DOT BELOW AND DOT ABOVE] and ṩ [U+0073 LATIN SMALL LETTER S, U+0307 COMBINING DOT ABOVE, U+0323 COMBINING DOT BELOW] implies that "s\u0361".localeCompare("\u1E69") and "s\u0361".localeCompare("s\u0307\u0323") must have the same sign.
• Canonical equivalence between ṩ [U+1E69 LATIN SMALL LETTER S WITH DOT BELOW AND DOT ABOVE] and ṩ [U+0073 LATIN SMALL LETTER S, U+0307 COMBINING DOT ABOVE, U+0323 COMBINING DOT BELOW] implies that "s\u0306".localeCompare("\u1E69") and "s\u0306".localeCompare("s\u0307\u0323") must have the same sign.
• Canonical equivalence between ṩ [U+1E69 LATIN SMALL LETTER S WITH DOT BELOW AND DOT ABOVE] and ṩ [U+0073 LATIN SMALL LETTER S, U+0307 COMBINING DOT ABOVE, U+0323 COMBINING DOT BELOW] implies that "s\u0308".localeCompare("\u1E69") and "s\u0308".localeCompare("s\u0307\u0323") must have the same sign.
• Canonical equivalence between ḍ̇ [U+1E0B LATIN SMALL LETTER D WITH DOT ABOVE, U+0323 COMBINING DOT BELOW] and ḍ̇ [U+1E0D LATIN SMALL LETTER D WITH DOT BELOW, U+0307 COMBINING DOT ABOVE] implies that "\u1E0C".localeCompare("\u1E0B\u0323") and "\u1E0C".localeCompare("\u1E0D\u0307") must have the same sign.
• Canonical equivalence between 가 [U+AC00 HANGUL SYLLABLE GA] and 가 [U+1100 HANGUL CHOSEONG KIYEOK, U+1161 HANGUL JUNGSEONG A] implies that "\u1680".localeCompare("\uAC00") and "\u1680".localeCompare("\u1100\u1161") must have the same sign.
• Canonical equivalence between 가 [U+AC00 HANGUL SYLLABLE GA] and 가 [U+1100 HANGUL CHOSEONG KIYEOK, U+1161 HANGUL JUNGSEONG A] implies that "\u1100\u1166".localeCompare("\uAC00") and "\u1100\u1166".localeCompare("\u1100\u1161") must have the same sign.