Need to fix all <scheme_name>_namelist.xml or CIME entry_id_pg.xsd to include input_pathname

Currently all scheme namelists have the same copy-pasted block describing the namelist XML, however this block

```
input_pathname
Only include this attribute to indicate that the variable
contains the pathname of an input dataset that resides in the
CESM inputdata directory tree. Note that the variables
containing the names of restart files that are used in branch
runs don't reside in the inputdata tree and should not be given
this attribute.
```

is incorrect.

`case.build` validates the scheme namelist XMLs against
```
/usr/bin/xmllint --noout --schema CAM-SIMA/cime/CIME/ParamGen/xml_schema/entry_id_pg.xsd
```

which does not define `input_pathname` so including one will actually error out
```
..._namelist.xml:9: element input_pathname: Schemas validity error : Element 'input_pathname': This element is not expected. Expected is one of ( desc, category, valid_values, group, values, standard_name, long_name, units, kind ).
..._namelist.xml fails to validate
```

Either all the scheme namelist.xml files need to be fixed to remove this block of text or `entry_id_pg.xsd` should be amended to add `input_pathname`

Inspect the scheme namelist XML files and CAM-SIMA/cime/CIME/ParamGen/xml_schema/entry_id_pg.xsd, then reproduce the failure with xmllint or case.build. Compare the input_pathname documentation and schema expectations, and verify that every scheme namelist XML passes validation without losing the intended metadata.

Written by the indexing model from the issue text.