New Sidebar tests + fix flaky tests

[kakRostropovich]

Add new tests for New Sidebar:

• Add Channels to Sidebar from the Left Menu
• Pin/Unpin tabs
• Close tabs (via context menu or close button)
• Hide sidebar when user goes to another channel (may be changed)
• Close tabs and close sidebar at the end
• Create sidebar automatically when user replies to message
• Add first small checking of work in sidebar inside of existing planer tests

Fix flaky tests:

• Image Original View test
• Merge Contacts test

_{Huly®: UBERF-8212}