Remind the user to generate a backup file

[mrose17]

Test plan

See #13504

Original issue description

If the user has not created a backup file within 1 week of bootStamp, generate a notification reminding them to do so, with a button that brings up the dialog. The usual rules apply: "don't remind me", "remind me later", etc.

[jasonrsadler]

@mrose17 @bradleyrichter
We have no way of knowing if an existing user has backed up their keys.
How should notifications be handled for existing users that update to new version?

Option 1:
This change should only work for new users (existing users that haven't backed up will not receive notification)

Option 2:
This change works for all users (which means existing users that have backed up will receive notification)

[srirambv]

@jasonrsadler mind updating the issue with verification steps.

[bsclifton]

@srirambv plan updated 👍

[srirambv]

Verified on Windows x64

• 0.22.712 e48c5ff
• libchromiumcontent 66.0.3359.139
• muon: 6.0.9

Verified with macOS 10.12.6 using

• 0.22.712 e48c5ff
• muon 6.0.9
• libchromiumcontent 66.0.3359.139

[srirambv]

Moving based on feedback triage discussion and assigning to @mandar-brave

[bsclifton]

Closing as the revert was reverted. Fix is contained in 0.22.712

[LaurenWags]

Verified with macOS 10.12.6 using

• 0.22.714 fa2fbca
• muon 6.0.9
• libchromiumcontent 66.0.3359.139

Verified on Windows x64

• 0.22.714 fa2fbca
• muon 6.0.9
• libchromiumcontent 66.0.3359.139