Pin AC TO 57.0.0 and remove feature flag for view downloads

[Amejia481]

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.

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4. the APK links should be on the left side of the screen, named for each CPU architecture

[eliserichards]

Looks great! Can't wait to use the new downloads features!

[codecov-commenter]

Codecov Report

Merging #14592 into master will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master   #14592      +/-   ##
============================================
+ Coverage     30.09%   30.11%   +0.01%     
- Complexity     1165     1168       +3     
============================================
  Files           444      444              
  Lines         17916    17914       -2     
  Branches       2333     2331       -2     
============================================
+ Hits           5392     5394       +2     
+ Misses        12148    12145       -3     
+ Partials        376      375       -1     

Impacted Files	Coverage Δ	Complexity Δ
...pp/src/main/java/org/mozilla/fenix/FeatureFlags.kt	100.00% <ø> (ø)	4.00 <0.00> (ø)
...rc/main/java/org/mozilla/fenix/FenixApplication.kt	7.36% <0.00%> (+0.04%)	5.00 <0.00> (ø)
...lla/fenix/components/toolbar/DefaultToolbarMenu.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...p/src/main/java/org/mozilla/fenix/home/HomeMenu.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...in/java/org/mozilla/fenix/settings/SupportUtils.kt	76.00% <0.00%> (+6.00%)	13.00% <0.00%> (+2.00%)

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[liuche]

Some failing tests, some that seem unrelated:
verifySearchEngineCanBeChangedTemporarilyUsingShortcuts
testDownloadNotification
saveLoginFromPromptTest
settingsMenuBasicsItemsTests

[rpappalax]

Some failing tests, some that seem unrelated:
verifySearchEngineCanBeChangedTemporarilyUsingShortcuts
testDownloadNotification
saveLoginFromPromptTest
settingsMenuBasicsItemsTests

@liuche we see this occasionally with A-C upgrades where some UI tests become unstable. If the test failures are intermittent and seem unrelated to the PR and are blocking, pls give us a heads-up (@AaronMT @sv-ohorvath @rpappalax). It looks like at least settingsMenuBasicsItemsTests may be a genuine failure but we can take a look if this is blocking

[liuche]

testStrictVisitProtectionSheet ✅
testStrictVisitContentNotification ✅
verifySearchEngineCanBeChangedTemporarilyUsingShortcuts * ✅
testDownloadNotification ✅
neverSaveLoginFromPromptTest ✅
settingsMenuBasicsItemsTests * ✅
verifyAddonsCanBeUninstalled ✅
videoPlaybackSystemNotificationTest ❌ (but looks like audioPlaybackSystemNotificationTest failed on master recently)

https://console.firebase.google.com/project/moz-fenix/testlab/histories/bh.66b7091e15d53d45/matrices/4695329555498279318

Pushing a PR real quick for * search engine tests broken by #13452

EDIT: thanks rpapa! I'm seeing a couple that are actually broken by removing twitter from the search engine defaults, so I can fix those and then dig into some of the other tests to make sure.

Just ran the following original failing tests from my local PR:
verifySearchEngineCanBeChangedTemporarilyUsingShortcuts ✅
testDownloadNotification ✅
saveLoginFromPromptTest ✅
settingsMenuBasicsItemsTests ✅

and updated the other test states.

[liuche]

lmao maven errors

[liuche]

verifyContextOpenLinkNewTab
audioPlaybackSystemNotificationTest (intermittent #14596 #14593)

since these seem unrelated, I'm going to cherry-pick these commits onto a release branch so we're not blocked, and CI can take it's time going green here.

[liuche]

RPC failure fetching docker: https://firefox-ci-tc.services.mozilla.com/tasks/AEvLdPx5QSa8fXvDxKmhGg/runs/0/logs/https%3A%2F%2Ffirefox-ci-tc.services.mozilla.com%2Fapi%2Fqueue%2Fv1%2Ftask%2FAEvLdPx5QSa8fXvDxKmhGg%2Fruns%2F0%2Fartifacts%2Fpublic%2Flogs%2Flive.log

[liuche]

maven failure: https://firefox-ci-tc.services.mozilla.com/tasks/eGT-8LKbTIuwSeLU5EnzUg/runs/0/logs/https%3A%2F%2Ffirefox-ci-tc.services.mozilla.com%2Fapi%2Fqueue%2Fv1%2Ftask%2FeGT-8LKbTIuwSeLU5EnzUg%2Fruns%2F0%2Fartifacts%2Fpublic%2Flogs%2Flive.log

[liuche]

🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉 🎉

[Amejia481]

Finally 🎉