New UI for audio playback and global audio player

Introduce new UI and behavior for playing audio attachments in
conversations. Previously, playback stopped unexpectedly during window
resizes and scrolling through the messages due to the row height
recomputation in `react-virtualized`.

With this commit we introduce `<GlobalAudioContext/>` instance that
wraps whole conversation and provides an `<audio/>` element that
doesn't get re-rendered (or destroyed) whenever `react-virtualized`
recomputes messages. The audio players (with a freshly designed UI) now
share this global `<audio/>` instance and manage access to it using
`audioPlayer.owner` state from the redux.

New UI computes on the fly, caches, and displays waveforms for each
audio attachment. Storybook had to be slightly modified to accomodate
testing of Android bubbles by introducing the new knob for
`authorColor`.

ACKNOWLEDGMENTS.md

@@ -1301,6 +1301,24 @@ Signal Desktop makes use of the following open source projects.
     licenses; we recommend you read them, as their terms may differ from the
     terms above.
 
+## lru-cache
+
+    The ISC License
+
+    Copyright (c) Isaac Z. Schlueter and Contributors
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+    IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
 ## memoizee
 
     ISC License