Refactored EK80 data XML parser and also removed the usage of `dict_to_dict` method

[praneethratna]

Fixes #468 by improving parsing for EK80 XML data and also removed the usage of dict_to_dict method, also Fixes #1184 and now 'PingSequence' XML datagram is parsed and stored in the output of open_raw.

CC @leewujung @emiliom

[codecov-commenter]

Codecov Report

Merging #1186 (30272ee) into dev (ce1e614) will decrease coverage by 4.88%. The diff coverage is 90.42%.

@@            Coverage Diff             @@
##              dev    #1186      +/-   ##
==========================================
- Coverage   81.89%   77.01%   -4.88%     
==========================================
  Files          67       19      -48     
  Lines        5887     3059    -2828     
==========================================
- Hits         4821     2356    -2465     
+ Misses       1066      703     -363     

Flag	Coverage Δ
unittests	77.01% <90.42%> (-4.88%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
echopype/convert/parse_base.py	87.86% <ø> (ø)
echopype/convert/set_groups_ek80.py	97.17% <100.00%> (ø)
echopype/convert/utils/ek_raw_parsers.py	56.28% <90.21%> (+0.89%)	:arrow_up:

... and 49 files with indirect coverage changes

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more