Implement real-time text streaming in AI Chat

[nullhook]

Currently, the AI Chat feature consumes HTTP responses that wait for the entire text to be generated before returning to the user. This can lead to a delay in the user's ability to see the words as it is being generated, which can impact the overall user experience.

It would be beneficial to implement real-time text streaming in the AI Chat feature. This would allow users to see the words being generated as they are typed, providing a more interactive and engaging experience

[petemill]

@nullhook please add test plan

[LaurenWags]

@rebron @nullhook could you please add the following required labels as necessary:

• QA/Yes or QA/No (if QA/Yes, please provide a manual test plan)
• release-notes/include or release-notes/exclude

Thanks!

[nullhook]

Added a test plan

[LaurenWags]

Removed QA/In-Progress, see discussion under https://bravesoftware.slack.com/archives/C04KPE0BUDU/p1688150893428279 and https://bravesoftware.slack.com/archives/C04KPE0BUDU/p1688882388478409 for more information.