refactor: use common base class for legacy and modern reader, move logic from nd2file

[tlambert03]

big internal refactor to cleanup and unify the protocol that legacy and modern readers use.

This also has legacy readers return a proper Metadata object

[codecov]

Codecov Report

Merging #160 (cba6f9b) into main (a86bb6d) will increase coverage by 0.22%.
The diff coverage is 91.42%.

@@            Coverage Diff             @@
##             main     #160      +/-   ##
==========================================
+ Coverage   93.66%   93.88%   +0.22%     
==========================================
  Files          16       17       +1     
  Lines        2272     2340      +68     
==========================================
+ Hits         2128     2197      +69     
+ Misses        144      143       -1     

Impacted Files	Coverage Δ
src/nd2/_binary.py	88.57% <ø> (-2.44%)	⬇️
src/nd2/_parse/_chunk_decode.py	87.40% <ø> (ø)
src/nd2/_parse/_clx_lite.py	91.50% <ø> (ø)
src/nd2/_parse/_clx_xml.py	89.36% <ø> (ø)
src/nd2/_parse/_legacy_xml.py	97.50% <ø> (ø)
src/nd2/_sdk_types.py	100.00% <ø> (ø)
src/nd2/index.py	97.58% <ø> (ø)
src/nd2/readers/protocol.py	90.14% <90.14%> (ø)
src/nd2/readers/_legacy/legacy_reader.py	90.34% <90.34%> (ø)
src/nd2/readers/_modern/modern_reader.py	92.02% <92.30%> (ø)
... and 7 more

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[codspeed-hq]

CodSpeed Performance Report

Merging #160 will not alter performances

_{Comparing reader-base (cba6f9b) with main (a86bb6d)}

Summary

✅ 13 untouched benchmarks