ChatView: make "stop" and "copy conversation" work again

[manyoso]

…gression

in a few places in QML that were using this method. This PR fixes two of these issues:

• Issue Stop generation button no longer works in v3.6.0 #3333 - the stop generation button no longer working
• Issue Copy of entire conversation broken in v3.6.0 #3335 - the copy entire conversation button no longer working

It also adds a fixme in the code for a third issue which is less of a priority:

• Issue Not sending complete data to datalake in v3.6.0 #3334 - not sending the conversation to the datalake.

[manyoso]

This doesn't add the <stopped> tag back which maybe it should? It also doesn't label the prompt and the responses so the copied conversation isn't so readable... maybe should add this even though it would be a behavior change?

In order to add the <stopped> back to it this would need to be a permanent field of ChatItem and serialized as such as the way it was being done before in Javascript would not preserve it across loads.

UPDATE: I tested and found that the <stopped> tag hasn't been working even as far back as 3.0.0 so it isn't germane to this change.

[manyoso]

Okay, comparing to the copy conversation in v3.5.3 it is clear this PR still needs work.... fixing.

[cebtenzzre]

Also, should add a changelog entry.