url: ensure getter access do not mutate observable symbols

PR-URL: https://github.com/nodejs/node/pull/48897
Refs: https://github.com/nodejs/node/pull/48891
Refs: https://github.com/nodejs/node/issues/48886
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>

test/parallel/test-whatwg-url-custom-searchparams.js

@@ -16,7 +16,9 @@ const normalizedValues = ['a', '1', 'true', 'undefined', 'null', '\uFFFD',
                           '[object Object]'];
 
 const m = new URL('http://example.org');
+const ownSymbolsBeforeGetterAccess = Object.getOwnPropertySymbols(m);
 const sp = m.searchParams;
+assert.deepStrictEqual(Object.getOwnPropertySymbols(m), ownSymbolsBeforeGetterAccess);
 
 assert(sp);
 assert.strictEqual(sp.toString(), '');