Always explicitly start test activity

[KovalevAndrey]

Description

Fixes #213

AppyxViewTestRule merges composeTestRule and ActivityTestRule to make it easier to use for the clients. However if we automatically start activity we see the crash with stacktrace:

(3) setContent was called before the ComposeTestRule ran. If setContent is called by the Activity, make sure the Activity is launched after the ComposeTestRule runs

To avoid this instead automatic activity launching we could start activity explicitly.

Check list

• I have updated CHANGELOG.md if required.
• I have updated documentation if required.