For #8312 - Show Top Sites in a ViewPager

[gabrielluong]

Fixes #8312

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.

After merge

• Milestone: Make sure issues finished by this pull request are added to the milestone of the version currently in development.

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[gabrielluong]

This follows the approach that is used in Firefox Lite mozilla-mobile/FirefoxLite@7d7be8e. The Top site layout is as follow:
HomeFragment RecyclerView -> ViewPager2 (displays the individual pages) -> RecyclerView (4 column grid) -> TopSiteItems

The PagerIndicator is reused from https://github.com/mozilla-tw/FirefoxLite/blob/32ddedf67826e13ae0c6dd3591117f5020daebd4/app/src/main/java/org/mozilla/rocket/home/topsites/ui/PagerIndicator.kt.

We removed the dependency on google_flexbox since that is no longer used.

The proper layout of the items and grid will be done in #13765.

[codecov-commenter]

Codecov Report

Merging #14116 into master will decrease coverage by 0.10%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master   #14116      +/-   ##
============================================
- Coverage     29.78%   29.67%   -0.11%     
+ Complexity     1135     1133       -2     
============================================
  Files           437      440       +3     
  Lines         17565    17616      +51     
  Branches       2280     2289       +9     
============================================
- Hits           5231     5227       -4     
- Misses        11950    12004      +54     
- Partials        384      385       +1     

Impacted Files	Coverage Δ	Complexity Δ
...fenix/home/sessioncontrol/SessionControlAdapter.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...la/fenix/home/sessioncontrol/SessionControlView.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ssioncontrol/viewholders/TopSitePagerViewHolder.kt	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...me/sessioncontrol/viewholders/TopSiteViewHolder.kt	100.00% <ø> (ø)	2.00 <0.00> (ø)
...sioncontrol/viewholders/topsites/PagerIndicator.kt	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...ntrol/viewholders/topsites/TopSitesPagerAdapter.kt	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...in/java/org/mozilla/fenix/settings/SupportUtils.kt	70.00% <0.00%> (-4.00%)	11.00% <0.00%> (-2.00%)

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[ekager]

r+ w nits