Create ToolbarPosition enum

[NotWoods]

Using an enum makes code much easier to read because the top/bottom association is more obvious. This just adds a new getter to Settings without changing the backing field.

        // Before
        val isBottomToolbar = Settings.getInstance(context).shouldUseBottomToolbar

        layout.drop_down_triangle.isGone = isBottomToolbar
        layout.pop_up_triangle.isVisible = isBottomToolbar

        // After
        val toolbarPosition = context.settings().toolbarPosition

        layout.drop_down_triangle.isVisible = toolbarPosition == ToolbarPosition.TOP
        layout.pop_up_triangle.isVisible = toolbarPosition == ToolbarPosition.BOTTOM

[codecov-commenter]

Codecov Report

Merging #12747 into master will increase coverage by 0.00%.
The diff coverage is 13.41%.

@@            Coverage Diff            @@
##             master   #12747   +/-   ##
=========================================
  Coverage     27.26%   27.26%           
- Complexity      963      965    +2     
=========================================
  Files           401      402    +1     
  Lines         15974    15969    -5     
  Branches       2033     2032    -1     
=========================================
- Hits           4355     4354    -1     
+ Misses        11291    11286    -5     
- Partials        328      329    +1     

Impacted Files	Coverage Δ	Complexity Δ
...a/org/mozilla/fenix/browser/BaseBrowserFragment.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...main/java/org/mozilla/fenix/cfr/SearchWidgetCFR.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...lla/fenix/components/toolbar/BrowserToolbarView.kt	2.83% <0.00%> (+0.11%)	0.00 <0.00> (ø)
...enix/components/toolbar/TabCounterToolbarButton.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...c/main/java/org/mozilla/fenix/home/HomeFragment.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...rg/mozilla/fenix/settings/CustomizationFragment.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../src/main/java/org/mozilla/fenix/utils/Settings.kt	61.11% <0.00%> (-0.15%)	25.00 <0.00> (ø)
...la/fenix/components/metrics/GleanMetricsService.kt	12.70% <33.33%> (ø)	4.00 <0.00> (ø)
.../java/org/mozilla/fenix/browser/BrowserAnimator.kt	7.69% <40.00%> (ø)	0.00 <0.00> (ø)
...ix/trackingprotection/TrackingProtectionOverlay.kt	77.55% <50.00%> (-0.89%)	10.00 <0.00> (ø)
... and 4 more

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[BranescuMihai]

I really like this cleanup initiative!

I would recommend creating tickets for any cleanup PRs though, as every time we touch code besides tests, there's a change we introduce regressions, so they should be tested.