[Docker] Add specific version for markupsafe (python package that gets usually installed when installing jupyter)

this commit moves all git repo-based dep cloning to ouside Docker,
and their installation commands to the entrypoint script

Made QuantIdentityHandler and FoldQuantWeights compatible with DebugMarker nodes and added QONNX to the test_brevitas_debug test.

Fixed a bug in the QuantReluHandler, where the export would fail if the activation was at the top of the network.