REF: more greppable names for ujson functions
Discussed with @WillAyd 
```
pandas/io/json/_table_schema.py:16: error: Module "pandas._libs.json" has no attribute "ujson_loads"  [attr-defined]
pandas/io/json/_json.py:24: error: Module "pandas._libs.json" has no attribute "ujson_dumps"  [attr-defined]
pandas/io/json/_json.py:24: error: Module "pandas._libs.json" has no attribute "ujson_loads"  [attr-defined]
pandas/io/excel/_xlsxwriter.py:264: error: Module has no attribute "ujson_dumps"  [attr-defined]
pandas/io/excel/_odswriter.py:250: error: Module has no attribute "ujson_dumps"  [attr-defined]
``` Thanks @jbrockmendel 