The new behavior is as follows:

IF a user has a token and `features` is not set, we treat it as if the
feature was enabled.

IF a user has a token and `features` is set, we check if the feature
name has a value of "true".

`isJwtFeatureEnabled` also provides a way to specify the default value
in case there is no token.

Also, ignore the toggle screenshare shortcut when the video sender limit is reached.

- add possibility to allow execution of the button's routine besides triggering
`toolbarButtonClicked` API event
- keep backwards compatibility
- get rid of `ToolbarButton`

* feat(toolbox) allow any toolbox button to be displayed as main

fixes the previous behaviour where only a certain set of buttons were whitelisted for being displayed in the main toolbar

* code review

* code review - fix avatar icon position