fix: update prov attributes combine

[lsetiawan]

Overview

This PR address Issue #1115. Now the code checks and keep track of current attributes data from each combined files that exists. This probably can be optimized in the future, but for now it fixes the bug.

[codecov-commenter]

Codecov Report

Merging #1116 (0a1bc9a) into dev (cd52645) will decrease coverage by 19.98%.
Report is 3 commits behind head on dev.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##              dev    #1116       +/-   ##
===========================================
- Coverage   78.27%   58.30%   -19.98%     
===========================================
  Files          65       13       -52     
  Lines        6265     1180     -5085     
===========================================
- Hits         4904      688     -4216     
+ Misses       1361      492      -869     

Flag	Coverage Δ
unittests	58.30% <100.00%> (-19.98%)	⬇️

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Files Changed	Coverage Δ
echopype/echodata/combine.py	80.80% <100.00%> (+2.22%)	⬆️

... and 54 files with indirect coverage changes

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[emiliom]

The PR looks great, thanks! It does what it's supposed to do.

In test_combine_echodata_combined_append I found a fair bit of code blocks (tests) that were nearly identical except and could be consolidated to use common code. So, I did that, plus a few other smaller improvements (IMHO) in readability, in this PR to your PR: lsetiawan#1
These changes are not needed, but I think they're helpful. Once you merge my PR (hopefully there won't be any problems), feel free to merge your PR.

[lsetiawan]

@emiliom please approve this PR so I can merge it. Thanks!