classfields: PrivateFieldSet and PrivateFieldGet

test/language/statements/class/privatefieldget-success-1.js

test/language/statements/class/privatefieldget-success-2.js

test/language/statements/class/privatefieldget-success-3.js

test/language/statements/class/privatefieldget-success-4.js

test/language/statements/class/privatefieldget-success-5.js

.../language/statements/class/privatefieldget-typeerror-1.js

.../language/statements/class/privatefieldget-typeerror-2.js

.../language/statements/class/privatefieldget-typeerror-3.js

.../language/statements/class/privatefieldget-typeerror-4.js

.../language/statements/class/privatefieldget-typeerror-5.js

.../language/statements/class/privatefieldset-typeerror-1.js

.../language/statements/class/privatefieldset-typeerror-2.js

.../language/statements/class/privatefieldset-typeerror-3.js

.../language/statements/class/privatefieldset-typeerror-4.js

.../language/statements/class/privatefieldset-typeerror-5.js