Enable tests for boot2qt

The tests for boot2qt were disabled with commit
cc7fb64d

. The tests can
be enabled since qtdeclarative now fallbacks to software
renderer if OpenGL is not supported.

Also some timings needed to be relaxed for the tests to
pass when running on Qemu.

Task-number: QTBUG-60268
Change-Id: I8f933511c956b728a76870231a58ed89398a75ba
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>