All instances of an FMS ID to the internal interpolation content is
replaced with a derived type containing additional metadata recording
the field's origin filename and fieldname.

This additional information is required in order to replicate the axis
data from the field, which is no longer provided by FMS2.

The abstraction of this type also allows us to either extend it or
redefine it in other frameworks as needed in the future.

This primarily affects the usage of the following functions:

- init_external_field
- time_interp_external
- horiz_interp_and_extrap_tracer

The following solvers are updated:

- MOM_open_boundary
- MOM_ice_shelf
- MOM_oda_driver
- MOM_MEKE
- MOM_ALE_sponge
- MOM_diabatic_aux

Of these, OBC was the most significant.  The integer handle (fid) was
previously used to determine if each segment field was constant or (if
negative) read from a file.  After being replaced by the derived type, a
new flag was added to make this determination.

All of the coupled drivers have been modified, since they support time
interpolation of T and S fields.

- FMS
- MCT
- NUOPC

The NUOPC driver also includes modifications to its CFC11 and CFC12
fields.  Changes to the MOM CFC modules replaces an `id == -1`-like
test, which is not used by the derived type.  This check has been
removed, and we now solely rely on the `present(cfc_handle)` test.

While this could change behavior, there does not seem to be any scenario
where init_external_field would return -1 but would be passed to the
function.  (But I may eat these words.)

With removal of axis-based operations in FMS2 I/O, this patch removes
references to these calls and replaces them with MOM `axes_info` types.
References to FMS1 read into an `axistype`, but the contents are
transferred to an `axis_info`.  FMS2 directly populates the `axis_info`
content.

The `get_external_field_info` calls are modified to return `axis_info`
rather than `axistype`.

The redundant `get_axis_data` function is also removed from
`MOM_interp_infra`, since `get_axis_info` provides an equivalent
operation.

Generally speaking, this is not an improvement of the codebase.  The
FMS1 layer does a redundant copy of data from `axistype` to `axis_info`.
The FMS2 layer is significantly worse, and re-opens the file to read the
axis data for each field!  But if the intention is to leverage the
existing API, then I don't think we have any choice at the moment.

Assuming this is a relatively infrequent operation, this should not
cause any measureable issues, but it needs to be watched carefully.

This patch shifts all remaining time_interp_external functions from
time_interp_external to equivalent ones in time_interp_external2.

Internally, time-interpolated fields are initialized with `ongrid` set
to `.true.`, and such fields are assumed to be on-grid.

This seems to hold for all existing instances of `time_interp_external`,
but needs to be monitored in the future somehow.

The FMS1 implementation of init_external_field is case-insensitive, but
the FMS2 implementation is case-sensitive, which can cause errors in
older established input files.

This patch sweeps through the fields of the input files and checks for a
case-insensitive match (using lowercase()).  This requires an additional
open/close of the file.

…_plume

- including now passing the dimensional scaling tests.

Tweaking the brine plume code.

- it now works better on restart

- I could move it up and make it not optional.