Rewards notifications are saved on shutdown only

[SergeyZhukovsky]

Description

Notifications like grants, auto contribution status are not stored in storage until we shutdown the browser properly. We can miss them if there is a crash and etc

Steps to Reproduce

1. Make sure you just received a notification above BAT icon
2. Kill browser process
3. Open browser again.

Actual result:

There is no notification

Expected result:

There is notification

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

any

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds?
  yes

Website problems only:

• Does the issue resolve itself when disabling Brave Shields?
• Is the issue reproducible on the latest version of Chrome?

Additional Information