We need a larger NC_MAX_NAME for cases of URLs in file names

[edwardhartnett]

I just noticed this change that @DennisHeimbigner made to tst_quantize.c to add nczarr testing:

#ifdef TESTNCZARR
	    char file_name[4096];
#else
	    char file_name[NC_MAX_NAME + 1];
#endif

What is happening here is that I am using NC_MAX_NAME (from netcdf.h), but that is set at:

#define NC_MAX_NAME 256

So this is apparently not long enough if URLs can be involved?

In that case I recommend we define, in nc_tests.h (not netcdf.h) NC_MAX_FILENAME to 4096, and then we can use that in tests.