feat: Process TSV files as streams and validate only the first 1000 rows by default

[effigies]

This PR is an optimization. In #138 we found a case with >300k lines in a TSV file. In order to limit the number of lines being inspected, I needed to switch TSV loading to be stream-based instead of slurping the entire file.

This PR does the following:

• Refactors the UTF8 enforcement of BIDSFileDeno.text into a stream transformer in files/stream.ts
• Rewrites loadTSV to process files as a stream.
  • UTF8 validation
  • Rechunk as lines of text, splitting on \r?\n
• Rewrites column loading as an array of pre-allocated arrays for efficiency. The ColumnsMap is constructed at the end.
• Adds a --max-rows flag to the CLI and a maxRows variable to validator options.

Note that this adds a new error condition, where we tolerate empty lines only at the end of files (<content><LF><EOF>). In passing, this permits us to report the line number of bad TSV lines.

I also do not attempt to add maxRows to the TSV cache key, so calling loadTSV() successively on the same file and different maxRows values will return the result from the first call. This does not seem like a problem in terms of running the validator, but might be surprising to future developers. I can look into that, if desired.

Closes #138.

[effigies]

This file in particular will be easiest to review just by reading the new file, as the contents are almost entirely new.