Closes #1472: Adding support for JavaScript confirm dialogs

[Amejia481]

Pull Request checklist

• Quality: This PR builds and passes detekt/ktlint checks (A pre-push hook is recommended)
• Tests: This PR includes thorough tests or an explanation of why it does not
• Changelog: This PR includes a changelog entry or does not need one

[codecov]

Codecov Report

Merging #1963 into master will increase coverage by 0.48%.
The diff coverage is 75.64%.

@@             Coverage Diff             @@
##             master   #1963      +/-   ##
===========================================
+ Coverage     83.61%   84.1%   +0.48%     
- Complexity     1939    2093     +154     
===========================================
  Files           255     262       +7     
  Lines          8148    8699     +551     
  Branches       1246    1299      +53     
===========================================
+ Hits           6813    7316     +503     
- Misses          814     841      +27     
- Partials        521     542      +21

Impacted Files	Coverage Δ	Complexity Δ
.../components/concept/engine/prompt/PromptRequest.kt	79.71% <0%> (-16.79%)	0 <0> (ø)
...ozilla/components/feature/prompts/PromptFeature.kt	93.25% <88.88%> (+0.13%)	52 <0> (+1)	⬆️
...nents/feature/prompts/MultiButtonDialogFragment.kt	89.58% <89.58%> (ø)	14 <14> (?)
...r/toolbar/behavior/BrowserToolbarBottomBehavior.kt	90% <0%> (ø)	11% <0%> (?)
...zilla/components/browser/toolbar/BrowserToolbar.kt	95.42% <0%> (ø)	55% <0%> (?)
...lla/components/browser/toolbar/edit/EditToolbar.kt	97.22% <0%> (ø)	7% <0%> (?)
...mponents/browser/toolbar/display/DisplayToolbar.kt	93.82% <0%> (ø)	40% <0%> (?)
...ts/feature/customtabs/AbstractCustomTabsService.kt	76.47% <0%> (ø)	9% <0%> (?)
...nts/feature/customtabs/CustomTabsToolbarFeature.kt	93.22% <0%> (ø)	17% <0%> (?)
... and 1 more

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[codecov]

Codecov Report

Merging #1963 into master will decrease coverage by <.01%.
The diff coverage is 88.46%.

@@             Coverage Diff              @@
##             master    #1963      +/-   ##
============================================
- Coverage     84.38%   84.37%   -0.01%     
+ Complexity     2150     2133      -17     
============================================
  Files           263      262       -1     
  Lines          8798     8794       -4     
  Branches       1310     1313       +3     
============================================
- Hits           7424     7420       -4     
+ Misses          829      828       -1     
- Partials        545      546       +1

Impacted Files	Coverage Δ	Complexity Δ
.../components/concept/engine/prompt/PromptRequest.kt	94.2% <83.33%> (-2.29%)	0 <0> (ø)
...ozilla/components/feature/prompts/PromptFeature.kt	93.25% <88.88%> (+0.13%)	52 <0> (+1)	⬆️
...nents/feature/prompts/MultiButtonDialogFragment.kt	89.58% <89.58%> (ø)	14 <14> (?)
...illa/components/service/glean/BooleanMetricType.kt	100% <0%> (ø)	9% <0%> (-6%)	⬇️
...ts/feature/customtabs/AbstractCustomTabsService.kt
...nts/feature/customtabs/CustomTabsToolbarFeature.kt

---

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