Fixed messages shown on extensions page - All Predefined Messages Should Be Replaced

[jonathansampson]

Test Plan:

Enable the Save to Pocket extension
Ensure that the description does not contain _MSG
Navigate to about:extensions
Ensure that Save to Pocket does not contain references to _MSG for Google Chrome

Original issue description

• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  Brave currently only looks for three specific values to handle when applying predefined messages in an extension's manifest. This could potentially miss several other keys that also need to be modified.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Desktop

• Brave Version (revision SHA):
  d4cad89

• Problem Code:
  

  browser-laptop/app/extensions.js

  Line 379 in b299cc6

  if (installInfo.name) {