[Cashtab] [Extension] [Code cleanup p4 retry] Update comments and function name for triggerUi

Summary:
T2751

Depends on D12545

Originally, triggerUi was modeled on a metamask generalist function. However in Cashtab it is only used for opening a window to send a prepopulated xec tx.

Update the comments and function name to reflect this.

Test Plan:
npm run extension
Update your local unpacked extension
Navigate to components.cashtab.com
Click on Cashtab Pay button for the standard Cashtab Badge component
Cashtab extension should open with tx populated

Reviewers: #bitcoin_abc, kieran709

Reviewed By: #bitcoin_abc, kieran709

Differential Revision: https://reviews.bitcoinabc.org/D12546