Infinite propagation of expressions from simplify

**Describe the bug**
When a simple assignment from an edge is propagated to a tasklets but is not removed because it is needed somewhere else. Then when another pass of propagation is done it propagates again the same assignment.

**To Reproduce**
Execute simplify on "test.sdfg" will produce the file "simplified.sdfg". After the simplify pass tasklet T9 has multiple times the same variable declaration. When the SDFG is compiled it fails because the variable "dace_i_0" is declared multiple times.
[test.zip](https://github.com/spcl/dace/files/10068840/test.zip)

**Expected behavior**
Do not add again the same code to the tasklet if it was already added. In this case it is actually also safe to remove the assignment on the edge but this is not always the case.

**Desktop (please complete the following information):**
- OS: Fedora Linux 35 (Workstation)
- DaCe: 0.14.1