tests: bsim: Bluetooth: Workaround Zephyr Controller scheduling overlap

Workaround test failures due to Zephyr Controller scheduling
overlap causing Periodic Advertising Sync timeouts, ACL
connection failed to be established or Controller assertion
when having latency at the CIS setup instant.

Workaround by using `-start_offset` to ensure that the ACL
established does not overlap the sink being established.

Relates to commit 490da9ec ("tests: bsim: Bluetooth:
Workaround overlapping ACL in BAP broadcast sink").

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>