Add TTL to Install Modal web QRCodes

# Feature Request
We are going to be integrating [MWP](https://github.com/MetaMask/mobile-wallet-protocol/blob/2b68eace15fbf6f9d85c01aa1024be50aeb087a2/docs/02-connection-flow.md) soon and we will require the install modal to do the following:

* To have the ability to regenerate the QRCode once the modal has been shown
* Add UI component to show the TTL, time to expir

### Why is this needed
The new QRCodes for remote connections are going to have limited TTL, around 60 seconds by default. This means a new QRCode will only be valid during that period.

We will also need to show a counter.

### To be decided
A) Regenerate the QRCode every time it reaches the TTL.
B) Show expired QRCode notice and a button to regenerate it

The issue does not name files or tests; start by locating the web install modal and its QRCode generation entry point. Clarify whether expiration regenerates automatically or shows an expired notice with a regeneration button, then define the TTL counter behavior and tests for expiration and regeneration.

Written by the indexing model from the issue text.