Add tests for contextual keywords with escape sequences

test/language/export/escaped-as-export-specifier.js

test/language/export/escaped-default.js

test/language/export/escaped-from.js

...anguage/expressions/async-arrow-function/escaped-async.js

test/language/expressions/async-function/escaped-async.js

test/language/expressions/async-generator/escaped-async.js

test/language/expressions/new.target/escaped-new.js

test/language/expressions/new.target/escaped-target.js

.../object/method-definition/async-gen-meth-escaped-async.js

...ions/object/method-definition/async-meth-escaped-async.js

...guage/expressions/object/method-definition/escaped-get.js

...guage/expressions/object/method-definition/escaped-set.js

test/language/import/escaped-as-import-specifier.js

test/language/import/escaped-as-namespace-import.js

test/language/import/escaped-from.js

test/language/statements/async-function/escaped-async.js

test/language/statements/async-generator/escaped-async.js

...language/statements/class/async-gen-meth-escaped-async.js

test/language/statements/class/async-meth-escaped-async.js

test/language/statements/class/syntax/escaped-static.js