Brave extension should be lazy and less memory intensive

[petemill]

Description

Brave extension background process is always in-memory, using up from 30mb - 150mb. This should be:

• Only ever 30mb in size, and not grow.
• Quit when not needed (not persistent)

In order for this to happen:

• Everything needs to be ok with the extension's memory being wiped out in-between events (i.e. persist stuff)
• Not load everything all at one time in to memory (i.e. every blocked resource list for every open tab)

[rebron]

cc: @cezaraugusto

[NejcZdovc]

+1 from #10702

[petemill]

Assigining multiple people as hopefully some of us can look at it after brave/brave-core#13638 with regards to greaselion / rewards API usage which prevent the extension process exiting periodically

[Miyayes]

I think this is resolved with the new WebUI-based Rewards panel? #22423 @petemill