1962 slack mention clone minor changes

[BazinC]

This PR includes minor changes we would like to get shipped with #2038.

• Enable providing custom edit request handlers by constructor
• Enable providing the trigger tby constuctor (default to '@')
• Make the removeSlackComposingTokenAttribution method public
• Provide a way to set value on the SlackTagIndex
• Replace print() statements with logger.
• Remove 2 AssertionError thrown when running on Android. They lead to the editor stuck in an unusable state. Removed because the situation happen without encountering any edge case. Normal usage.

[BazinC]

@matthew-carroll let me know if it is possible to merge this into your branch

[matthew-carroll]

Looks like a bunch of tests are failing. I'll make the changes you listed directly on my branch.

In general, there's no reason to put up a PR to change a branch that someone is already working on. In this case, I would have preferred that you just tell me what you want me to adjust.

[BazinC]

Understood