Make sure cooler::File::close() does not attempt to finalize files twice

[robomics]

Finalizing .cool files more than once does not do any harm, however it can result in "scary" warnings such as

The following error occurred while closing file /tmp/4DNFIYECESRC.50000.cool: Unable to create the attribute "assembly": (Attribute) Object already exists
File is likely corrupted or incomplete

So it is best if once finalize() has been called, the _finalize flag is set to false before the file handle is closed for real.

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.

Project coverage is 79.25%. Comparing base (cda8f37) to head (76384dd).
Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
...ctk/cooler/include/hictk/cooler/impl/file_impl.hpp	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #291      +/-   ##
==========================================
- Coverage   79.33%   79.25%   -0.08%     
==========================================
  Files         173      173              
  Lines       17003    17012       +9     
  Branches     2309     2309              
==========================================
- Hits        13489    13483       -6     
- Misses       2513     2522       +9     
- Partials     1001     1007       +6     

Flag	Coverage Δ
[tests	integration](https://app.codecov.io/gh/paulsengroup/hictk/pull/291/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=paulsengroup)	69.71% <90.90%> (-0.06%)
[tests	unittests](https://app.codecov.io/gh/paulsengroup/hictk/pull/291/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=paulsengroup)	77.25% <90.90%> (-0.16%)

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