Remove confirmTransaction Redux state for non-transaction confirmations

[Gudahtt]

The confirmTransaction Redux state serves only to store gas configuration during gas confirmation. However, we have many types of confirmations that don't involve gas (signatures, encryption, etc.). We use this same confirmTransaction Redux state for these transactions despite it serving no purpose, which further complicates the confirmation UI.

We should simplify the confirmation UI by refactoring the confirmation components to ensure this state is only used for transactions, where it serves an actual purpose. Any confirmations without gas can derive their state directly from the background state.

See here for more context: #10350 (comment)