As discussed in a netcdf meeting, convert NCZarr V2 to store all netcdf-4 specific info as attributes. This improves interoperability with other Zarr implementations by no longer using non-standard keys.
## Other Changes
* Remove support for older NCZarr formats.
* Update anonymous dimension naming
* Begin the process of fixing the -Wconversion and -Wsign-compare warnings in libnczarr, nczarr_test, and v3_nczarr_test.
* Update docs/nczarr.md
* Rebuild using the .y and .l files
re: https://github.com/Unidata/netcdf-c/issues/2189
Compression of a variable whose type is variable length
fails for all current filters. This is because at some point,
the compression buffer will contain pointers to data instead
of the actual data. Compression of pointers of course is meaningless.
The PR changes the behavior of nc_def_var_filter so that it will
fail with error NC_EFILTER if an attempt is made to add a filter
to a variable whose type is variable-length.
A variable is variable-length if it is of type string or VLEN
or transitively (via a compound type) contains a string or VLEN.
Also added a test case for this.
## Misc Changes
1. Turn off a number of debugging statements