Ensōgen with latest Ensō API

[glass-hash]

This PR adds support for ensogen with the latest Ensō userspace library. Overview of the changes made:

1. Updated the TX/RX functions to use the newer abstractions - TxPipe, RxPipe, Device.
2. Minor changes to enhance code readability - added macros wherever possible.
3. Fix for an issue where the RX stats were incorrect for 1518 packet sizes (see helpers.cpp).
4. Enhanced load_bitstream.sh to automatically download the bitstream in case it is not present.

Testing performed:

1. Verified throughput in echo server by using 64 and 1518 packets.
2. Verified that the count option works properly.
3. Verified the changes made in load_bitstream.sh.

Edit: Change number 3 listed above was dropped in the latest changes.

[hsadok]

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