feat: add ome_metadata output to ome-types

[tlambert03]

A start to support ome-metadata output

with nd2.ND2File('myfile.nd2') as f:
    ome = f.ome_metadata()  # instance of ome_types.OME

# then to get xml.....
ome.to_xml()

[codspeed-hq]

CodSpeed Performance Report

Merging #153 will not alter performances

_{Comparing ome (4f79fa2) with main (c0f1c78)}

Summary

✅ 13 untouched benchmarks

[codecov]

Codecov Report

Merging #153 (4f79fa2) into main (c0f1c78) will increase coverage by 0.21%.
The diff coverage is 98.11%.

@@            Coverage Diff             @@
##             main     #153      +/-   ##
==========================================
+ Coverage   93.28%   93.49%   +0.21%     
==========================================
  Files          15       16       +1     
  Lines        2220     2261      +41     
==========================================
+ Hits         2071     2114      +43     
+ Misses        149      147       -2     

Impacted Files	Coverage Δ
src/nd2/__init__.py	100.00% <ø> (ø)
src/nd2/_pysdk/_parse.py	93.77% <ø> (+0.28%)	⬆️
src/nd2/_ome.py	97.72% <97.72%> (ø)
src/nd2/_clx_xml.py	89.36% <100.00%> (ø)
src/nd2/_legacy/_legacy_xml.py	97.50% <100.00%> (ø)
src/nd2/_pysdk/_pysdk.py	91.79% <100.00%> (+0.34%)	⬆️
src/nd2/nd2file.py	95.55% <100.00%> (+0.02%)	⬆️
src/nd2/structures.py	96.08% <100.00%> (+0.01%)	⬆️

... and 2 files with indirect coverage changes

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