`<symbol> in <ClassRef>` misses static symbol members

[proggeramlug]

Summary

<symbol> in <ClassRef> returns false for symbol-keyed static members,
whereas Node returns true.

Repro

class D { static [Symbol.hasInstance]() { return false; } }
console.log(Symbol.hasInstance in D);   // node: true   perry: false

class K {}
const s = Symbol.for("t");
(K as any)[s] = 1;
console.log(s in K);                    // node: true   perry: false

Notes

Pre-existing, separate from the string-key class-ref fix (#6149 / PR #6159).
Symbol keys are intercepted early in js_object_has_property by the symbol
path (js_object_get_symbol_property), which doesn't resolve a class ref's
static symbol methods or runtime C[sym] = … assignments. Both a declared
static [Sym]() {} and a runtime symbol assignment on a class ref are missed.