[Feature Request] - `MockComponent::query_ref` query without cloning

[hasezoey]

Description

While putting together #120 and some other things, i noticed that it is unnecessary that MockComponent::query returns a value that is not a reference.
This keep this backwards compatible, this could be implemented as a new optional function.

Changes

When wanting to keep backwards compat, add a new optional function that has the signature of:

fn(&self, attr: Attribute) -> Option<&AttrValue>;

If not wanting backwards compat (ie a new major version), consider changing query directly.

For reference, the following is the current (as of 3.1.0 definition):

tui-realm/src/core/component.rs

Line 30 in 10923d2

fn query(&self, attr: Attribute) -> Option<AttrValue>;

[hasezoey]

Now that i am thinking more about this, changing to return type Option<&AttrValue> would make it more annoying to store variables without the AttrValue wrapper.
Maybe it would be a good idea to introduce AttrValueRef which is basically AttrValue but the values in it are references instead of the values themself.

Also, if it is changed, should be a query_mut also be added? If that would be the case, then we would also need a analogue AttrValueMut.