Exclude metamask dll from iOS after every reimport

[kantagara]

Describe the bug
Currently, after each setup.sh run, we have to manually exclude Chainsafe.Gaming.Metamask.dll from the platform so that our iOS can compile properly (if we're on a version higher than 2022.3.11) 😄 because we are deleting the .meta files for all the dlls for our Chainsafe.Gaming solution.
Solution is to add a simple asset preprocessor to the UnitySampleProject (and NOT in the package itself), so that we can exclude (or include) platforms for certain dlls
Steps
Steps to reproduce the behavior:

1. Run setup.sh
2. Try to build iOS on any version of Unity newer than 2022.3.10
3. Notice the compile error.

Expected behavior
iOS should compile normally