FIX: Shadow size property of columns object, so it acts as a column

[effigies]

Fixes #1824. This is a narrow fix for the size column. I believe the other things that could potentially be shadowed are:

• length
• entries
• keys
• hasOwnProperty
• constructor
• prototype
• toString

length is the only one that seems plausible to eventually have as a header, but it is not defined in BIDS, so I'm inclined to leave it alone for now.

I add a test that size is permissible and returns a column if present and returns undefined like other absent columns if absent.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (934c857) 85.97% compared to head (ac49a6e) 83.57%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1855      +/-   ##
==========================================
- Coverage   85.97%   83.57%   -2.40%     
==========================================
  Files         131       92      -39     
  Lines        6268     3897    -2371     
  Branches     1527     1273     -254     
==========================================
- Hits         5389     3257    -2132     
+ Misses        772      542     -230     
+ Partials      107       98       -9     

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[effigies]

This seems to be causing leaks:

valid_dataset dataset ... completes validation => ./src/tests/local/common.ts:26:11
error: Leaking async ops:
  - 2 async operations to op_read were started in this test, but never completed.
To get more details where ops were leaked, run again with --trace-ops flag.

valid_dataset dataset ... correctly ignores .bidsignore files => ./src/tests/local/valid_dataset.test.ts:10:11
error: Leaking resources:
  - A file (rid 400) was opened before the test started, but was closed during the test. Do not close resources in a test that were not created during that test.
  - A file (rid 401) was opened before the test started, but was closed during the test. Do not close resources in a test that were not created during that test.

valid_filenames dataset ... completes validation => ./src/tests/local/common.ts:26:11
error: Leaking async ops:
  - 2 async operations to op_read were started in this test, but never completed.
To get more details where ops were leaked, run again with --trace-ops flag.

valid_filenames dataset ... correctly ignores .bidsignore files => ./src/tests/local/valid_filenames.test.ts:10:11
error: Leaking resources:
  - A file (rid 37) was opened before the test started, but was closed during the test. Do not close resources in a test that were not created during that test.
  - A file (rid 38) was opened before the test started, but was closed during the test. Do not close resources in a test that were not created during that test.

valid_headers dataset ... completes validation => ./src/tests/local/common.ts:26:11
error: Test failed
error: Leaking async ops:
  - 1 async operation to op_read was started in this test, but never completed.
To get more details where ops were leaked, run again with --trace-ops flag.

valid_headers dataset ... correctly ignores .bidsignore files => ./src/tests/local/valid_headers.test.ts:10:11
error: Leaking resources:
  - A file (rid 31) was opened before the test started, but was closed during the test. Do not close resources in a test that were not created during that test.

[effigies]

@rwblair @nellh I was wrong, those leaking resources are not related to this PR but are happening in master. I think this is good to go, but we've got a separate problem on our hands.