Rebase onto servant

• Delete redundant code

• Remove test code that delete local echo failed

• Delete trailing newline

Handle the case where find_if returns localEchoes.end(), and update related test

In D143#2771, @tusooa wrote:

otherwise looks good

• Use MockHelper and deepEqual for test

• Use eventId instead of timeline index

• Add test

• Use index instead of eventId, fix cant display local echo in confirm popup

• Distinguish between events and local echo, add tests
• rebase onto servant

• Fix a error arguments format

• Use eventId instead of eventView for signal deleteEventRequested

• Use component for delete event confirm popup
• Add event content for delete event confirm popup
• Fix test

Rebase onto servant

Rebase onto D123

In D123#2379, @nannanko wrote:

• Add tests for room list priority

• Add tests for room list priority

Rebase onto servant

• Fix translation error
• Fix test

Make the resend button a ToolButton

Fix test for resend button

Make the resend button a ToolButton

Why should users be prevented from sending empty messages?