Editorial: Fix "property name" autolinking

[gibson042]

• Add "property names" as an alias.
• Use <emu-not-ref> to exempt "Unicode property name" and similar externally-defined concepts (which are currently inappropriately linked to the ECMAScript "property name" term throughout the Regular Expression section).
• Adjust <emu-not-ref>s to fully wrap such phrases (for less disruption of searching in source text).

[michaelficarra]

I would prefer to <dfn> "Unicode property name" (and add the qualifier "Unicode" in some cases) to avoid many of these <emu-not-ref>s.

[gibson042]

I would prefer to <dfn> "Unicode property name" (and add the qualifier "Unicode" in some cases) to avoid many of these <emu-not-ref>s.

I really don't think we should do that, because in ECMA-262 it is generally a reference to a specific column in the tables of UnicodeMatchProperty, which omit many of the properties actually encompassed by UTS #18 and would therefore have a high risk of misleading readers. If anything, I'd rather drop "name" from the column headings such that e.g. the columns become "Unicode property or property alias" and "Canonical representation" and references to them do not contain any "property name" substring which might be subject to autolinking.