Fstd2nc

* Further fixes for some 'Y' grid files, which were being
misidentified as 2D fields after the updates in the previous version.
* Fixed generate case where there is a single lat/lon point in the
file.
* Added documentation for string arguments to --filter option.

* Added quiet=True option for Buffer interface, similar to --quiet
option from command-line.
* Added some 'yin' and 'yang' projection metadata to files on a
yin-yang grid.
* Fixed data type for north_pole_grid_longitude (double instead of
int64).
* Added --decoder option for choosing method of reading the FST files.
(experimental).
* Persist last file opened for I/O, which may speed up accessing
multiple records from the same file.
* Allow fstdump to take multiple input file arguments. Previously
this could only be hacked in with globbing patterns surrounded in
quotes.
* Fix missing lat/lon coordinates for some 'Y' grid files.

* More bug fixes for RSF support.
* Fixed auto-detect of legacy FST files in xarray.open_dataset.
This was broken in 0.20240401.1 after adding RSF detection.
* Fixed crash when using --interp and --turbo features at the same
time.
* Fixed --crop-to-smallest grid not working in some cases.
decodeGrid was sometimes changing ig1/ig2/ig3 identifiers and causing
a failure to find common grids.

* Fixed crash when importing fstd2nc.extra without having rpnpy or
librmn in the environment.
* Some fixes for RSF support. Detect more recent variants of header
structures (e.g. for librmn 20.1.0-alpha3 snapshot).
* Fixed missing auto-detect for RSF in xarray interface.
* Fixed address overflow issue with CCC file interface, which was
giving missing data for larger files.

* Some support for new RSF file container and fst24 data format.
* Fixed bug in fstpy bridge - nk no longer stored in Buffer.
* Fixed check for operational dictionary when opdict=True is used in
Python interface.
* Added _CRS attribute to xarray interface.
* Fixed bug when using dask distributed - the keys were not integers,
but rather numpy integers, which apparently was a problem.
* Some support for mask typvar '!'.
* Fix potential bug if used in future librmn release 20.1 - the
call signature for armn_compress now requires an extra 'swap_stream'
argument to control byte swapping of the decoded values.

* Fixed a bug in open_index() when the index contains pickled data.
* Fix some bugs in vertical bounds (when --bounds is used).
* Added some more fields to the list of accumulated quantities.
* Fix a bug when using .from_fstpy() followed by .to_xarray() on
a single record.