Allow for disabling testnet mode by pressing the banner

[seanstrom]

Feature Issue

User Story

As a user,
I want to be able to enable and disable the testnet mode from the network settings inside the wallet settings.

Description

Implement the testnet mode UI toggle for displaying the testnet banner globally through the app.

Designs

Figma flow: the Figma designs

Acceptance Criteria

Screen	Description
	Users can tap the global Testnet mode banner to disable Testnet mode.
	Users are required to confirm that they want to disable Testnet mode.
	Users should see the Testnet mode banner disappear after disabling the Testnet mode banner.