fix: ensure ZipStore is open before acquiring lock

[oelhammouchi]

Fix a bug where ZipStore complains that it has no attribute _lock when some methods are called. Any method using the lock should make sure the store is opened because that's when the _lock attribute gets set.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.94%. Comparing base (7d8105f) to head (64940a1).

Files with missing lines	Patch %	Lines
src/zarr/storage/_zip.py	50.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3593      +/-   ##
==========================================
- Coverage   61.95%   61.94%   -0.02%     
==========================================
  Files          86       86              
  Lines       10170    10182      +12     
==========================================
+ Hits         6301     6307       +6     
- Misses       3869     3875       +6     

Files with missing lines	Coverage Δ
src/zarr/storage/_zip.py	70.39% <50.00%> (-1.47%)	⬇️

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[d-v-b]

how did the bug you are fixing here get past the store tests? Maybe we need to make those tests stronger?

[oelhammouchi]

You're right, I didn't want to appear presumptuous but the code could do with some refactoring as well, having to repeat all those _sync_open calls in so many functions naturally increases the probability of forgetting some. Not sure if this should be done in this PR though.

[d-v-b]

if you can find a clean way to reduce the repetition (e.g., a decorator) we'd appreciate it!