Co-authored-by: isabel rios <isabelrios@MacBook-Pro-de-isabel-2.local>

Stricter synchronization by always using the same "loadedSearchEngines"
variable.
With "loadedSearchEngines" calling "refreshAsync()" we also get the fallback
engines to contain reddit and youtube (which are programatically added) and
also now we properly remember and display the engines added by user.

* Re-enable codecov

* Use local script

* Revert to old codecov script

We have two search engine types:
- one based on MLS reported region,
- one based only on Locale.

There are multiple steps involved in returning the default search engine for
example and though at each step we could verify if a certain operation is
completed we are still exposed to concurrency issues.
Simplest and most effective way to make sure the MLS engines do not mix with
Locale based engines is to use the same type of engines for the entire duration
of the app. At the next cold start we'll verify again which engines to use.

Using the Locale based engines (fallbacks) is expected to only happen once, at
the first run of the application after being installed.

* For #11655: add leanplum event for installing an addon

* Add link to data-review request in PR

* Addressed CI comments

Without this line, the tests fail when running the full suite (but not
this test in isolation, for some reason).

Co-authored-by: Tiger Oakes <contact@tigeroakes.com>

* Add lints in Checks panel for test/lint tasks

* Switch to custom task

* Rename github tasks

Set the collection delete dialog title text to "Delete %1$s?"