Full blackboxing lines functionality

See link in https://bugzilla.mozilla.org/show_bug.cgi?id=1690450#c8 for discussions that have been had around blackboxing

This patch includes the following:-

• The reducer logic to store the blackbox url and range info matches that on the
  server here https://searchfox.org/mozilla-central/rev/dfc0dea63a16b73078a46b6ae49b2a626b8c11b5/devtools/server/actors/utils/sources-manager.js#289-335
  Note: The client logic supports multiple ranges whhile the server supports one range (maybe we can add support for multiple to the server).

• Added jest tests for some edge cases

• Changed the asyncStore pref from tabsBlackBoxed to blackboxedTabs for readability ease
  and to avoid and errors as the format of the data stored changes.

  Before: asyncStore.tabsBlackBoxed = ["foo.com", "bar.com"...]
  After: asyncStore.blackboxedTabs = { "foo.com": [], "bar.com": [range, range, ...] }

  The range sturcture

  const range = {
    start: { line: 1, column: 5 },
    end: { line: 3, column: 4 },
  }
  

https://hg.mozilla.org/mozilla-central/rev/7fe99e8b226c
https://hg.mozilla.org/mozilla-central/rev/fb36d632474d