Bug 1836482 - Replace AddonManager.jsm imports with AddonManager.sys.mjs r=Standard8,webcompat-reviewers,twisniewski

This patch was generated as follows:

Run:
`./mach esmify --imports . --prefix=toolkit/mozapps/extensions/AddonManager`
In the output there are linter/prettifier errors due to unused
XPCOMUtils or separate importESModule calls. These have been fixed
manually and verified with `./mach lint --outgoing`.

The `esmify` script also inserts many unwanted newlines around imports
that are broken on two lines due to length. Due to the number of these,
I fixed them programatically.

1. Create patch from the changes so far.
2. From the patch, delete all lines that consist of "+" (i.e. added blank line).
3. Reset the working dir and apply the revised patch.
4. Verify that the diff between step 1 and 3 looks reasonable.
5. Verify that this patch as a whole looks reasonable.

Commands:

```
git diff > rename.diff
:%g/^+$/d
git commit -va -m WIP-rename
git revert HEAD
git apply --recount rename.diff
git diff HEAD^  # and verify that the removed lines are ok.
git commit -va  # one last review to verify correctness of whole patch.
git rebase -i HEAD~3  # drop the WIP + reverted commit, pick only the last.
```

`git apply` has the `--recount` option to force it to ignore mismatches
in line counts, which happens because we deleted added lines (^+$)
without fixing up the line counts in the file headers.

Differential Revision: https://phabricator.services.mozilla.com/D179874