filter ignored top sites immediately after user interaction

[cezaraugusto]

address #12435
fix #10411

Test plan:

1. Excluding a website should exclude it immediately
2. Excluding a pinned website should exclude it immediately
3. Undo excluding should display the website again (note: it will go back to its original position at the moment it was excluded)
4. Undo excluding of a pinned website should display the website again but not pinned anymore
5. Excluding several websites and restoring all of them should restore all of them gracefully

[codecov-io]

Codecov Report

Merging #12635 into master will decrease coverage by 0.03%.
The diff coverage is 7.69%.

@@            Coverage Diff             @@
##           master   #12635      +/-   ##
==========================================
- Coverage   56.24%    56.2%   -0.04%     
==========================================
  Files         278      278              
  Lines       27115    27119       +4     
  Branches     4392     4392              
==========================================
- Hits        15250    15243       -7     
- Misses      11865    11876      +11

Flag	Coverage Δ
#unittest	56.2% <7.69%> (-0.04%)	⬇️

Impacted Files	Coverage Δ
js/about/newtab.js	40.95% <0%> (-2.06%)	⬇️
app/browser/api/topSites.js	94.28% <100%> (-0.26%)	⬇️
app/common/state/aboutNewTabState.js	94.87% <0%> (-5.13%)	⬇️

[bsclifton]

Works as expected 😄 👍 Very nice!

[bsclifton]

master dbec491
0.21.x 5a99f4d
0.20.x cbff8c5