Fix Percy tests to have them take snapshots of all content of the viewport

[luixxiul]

Steps to reproduce

This PR matrix-org/matrix-react-sdk#10343 has added Percy tests to have them take snapshots of viewport to check whether a long string does not overflow something.

• Long strings with a reply on IRC
• Long strings with a reply on modern layout
• Long strings with a reply on bubble layout

It turns out that they do not work as intended. The snapshots should be taken after scrolling to the bottom of the timeline, so that they can capture EventTiles with replies, etc.

Outcome

What did you expect?

The tests should take snapshots of all content of the viewport, not only the header and introduction of the room but also EventTiles below them.

The test should include a step to check whether elements which should be captured are visible on viewport before taking each snapshot.

What happened instead?

They took snapshots of a viewport which is supposed to be displayed to users initially.

Operating system

No response

Browser information

No response

URL for webapp

No response

Application version

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Homeserver

No response

Will you send logs?

No