* Adds in memory log storage, to be used while testing.

Enabling it only when config.debug is set, a configuration provided by jitsi-meet-torture.

* Moves to using config.testing.testMode property for logs storage.

* Fixes comments.

When _setLoggingConfig is invoked for the first time old and new config
are equal and _initLogging is not called. Currently, there is no way to
detect when the first time we call it is. We could use APP.logCollector
but it should go away at some point in the future.

The counterpart of the external API in the Jitsi Meet Web app uses the
search URL param jwt to heuristically detect that the Web app is very
likely embedded (as an iframe) and, consequently, needs to forcefully
enable itself. It was looking at whether there was a JSON Web Token
(JWT) but that logic got broken when the JWT support was rewritten
because the check started happening before the search URL param jwt was
parsed.

The functionality around logging including logging_config.js i.e.
loggingConfig and the other classes and/or functions that initialize
loggers for Jits Meet truly deserves a feature of its own. Start getting
in that direction on both Web and mobile by introducing
features/base/logging and bringing loggingConfig to mobile.