fix: LegacyHandler should provide unfrozen options to Adapters

[kiosion]

Description

This PR addresses an issue with the LegacyHandler in 4.12 - The StoreRequestContext obj passed to legacy Adapters is frozen, causing issues when modifying request params, i.e., modifying the query param within an Adapter's query or urlForQuery methods. I've added a failing test case as a reproduction of how I ran into this issue.

Notes for the release

[amk221]

Thanks. I'm also experiencing this from:

urlForQuery(query) {
  let url = super.urlForQuery(...arguments);

  if (query.something) {
    url = `${url}/${query.something}`;
    delete query.something;
  }

  return url;
}

this.store.query('foo', {
  something: 'abc'
});

The actual URL used will be /foo/abc?something=abc

But it should be /foo/abc