Optimization Opportunities in extensionState

[jonathansampson]

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

• Describe the issue you encountered:
  The extensionState module can be optimized in many places.

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

• Brave Version (revision SHA):
  0.19.1

• Steps to reproduce:
  N/A

• Actual result:
  N/A

• Expected result:
  N/A

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes

• Is this an issue in the currently released version?
  Yes

• Can this issue be consistently reproduced?
  Yes

[luixxiul]

I added release-notes/include as I thought every perf improvement should be mentioned :-)