Add the ability to modify a selectKit's content with `replaceContent`
Eg.
```
api.modifySelectKit("combo-box").replaceContent(() => {
return {
id: "foo",
name: "Foo",
};
});
```
will override existing content to only include the passed object
This reverts commit 20780a1eee.
* SECURITY: re-adds accidentally reverted commit:
03d26cd6: ensure embed_url contains valid http(s) uri
* when the merge commit e62a85cf was reverted, git chose the 2660c2e2 parent to land on
instead of the 03d26cd6 parent (which contains security fixes)
