Refactor templates to assert valid private accessor method names

src/accessor-names/private-escape-sequence-ZWJ.case

src/accessor-names/private-escape-sequence-ZWNJ.case

src/accessor-names/private-escape-sequence-u2118.case

src/accessor-names/private-escape-sequence-u6F.case

src/accessor-names/private-name-ZWJ.case

src/accessor-names/private-name-ZWNJ.case

src/accessor-names/private-name-common.case

src/accessor-names/private-name-dollar.case

src/accessor-names/private-name-u2118.case

src/accessor-names/private-name-underscore.case

src/accessor-names/private/cls-private-decl-inst.template

src/accessor-names/private/cls-private-decl-static.template

src/accessor-names/private/cls-private-expr-inst.template

src/accessor-names/private/cls-private-expr-static.template