tests: Bluetooth: Mesh: Add tests for BLOB Transfer in Pull mode

This commit adds several BabbleSim tests for BLOB transfer:
- A sanity test checking that BLOB Transfer completes successfully in
both, Push and Pull modes that runs transfer for 4 targets
- blob_cli_trans_resume test for Pull mode
- Test checking that BLOB client continues BLOB transfer if one of
targets times out while sending chunks.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>