Added parser support for EK80 MRU1

[praneethratna]

Addresses #1239 and now EK80 files of type MRU version 1 can be parsed.

CC @leewujung

[jmjech]

I e-mailed a 2 MB file to Wu-Jung. Let me know if it works for you. I have other "smaller" files. For some reason it is not allowing me to add the data files here.

[leewujung]

@jmjech: Thank you! The file works and does contain MRU1 datagrams.

@praneethratna: I have added this file (20231016_Cal_-D20231016-T220322.raw) under test_data/ek80. Could you please add a test for parsing it? In looking into this file I also checked for:

np.all(echodata["Platform"]["pitch"].data == np.array(parser.mru["pitch"]))
np.all(echodata["Platform"]["roll"].data == np.array(parser.mru["roll"]))
np.all(echodata["Platform"]["vertical_offset"].data == np.array(parser.mru["heave"]))  # note variable name change

Would be good to have these in the tests, by using the parser object https://github.com/OSOceanAcoustics/echopype/blob/03e3b52bb522222f5cdf887b6f519e47d4aae6bf/echopype/convert/api.py#L423

Thanks!!

[leewujung]

Also, on storing the heading variable. It is indeed in the ver.1 convention as below:

---

@praneethratna: Could you please add this to the set group so that it gets stored together with the other variables? As you have seen, they are on the same timebase since they are all from the MRU* datagrams. Make sure to add the attributes listed. Thanks!

[praneethratna]

@leewujung I have added docstring for new MRU1 type datagram and also added a new test case for the same using the file given by @jmjech. Also, now the heading variable will be stored in Platform group with the attributes that you've mentioned. Thanks!

[jmjech]

Thanks! I will test the code on my computer and let you know if I have any issues.