Refactor ingestion, save and load functions

[miratepuffin]

After the merge of #2391 we will have the following functions:

• load_edges
• load_nodes
• load_edge_metadata
• load_node_metadata

These will handle any dataframe inputs including (tested):

• Pandas dataframes
• FireDucks(.pandas) dataframes
• Polars dataframes
• Arrow tables
• DuckDB (eg. DuckDBPyRelation obtained from running an SQL query)

In addition to this, we should modify the function to internally check if the user has provided a dataframe or a filepath as an argument and transparantly handle loading from this if possible. Through this we can remove the following functions as they would be rolled into the above:

• load_edge_props_from_pandas
• load_edge_props_from_parquet
• load_edges_from_pandas
• load_edges_from_parquet
• load_node_props_from_pandas
• load_node_props_from_parquet
• load_nodes_from_pandas
• load_nodes_from_parquet

To reduce confusion we will change the following:

• load_from_file -> load_graph
• save_to_file -> save_graph
• save_to_zip -> flag on save_graph (to be discussed)

Post v4 merge the following functions will be removed:

• from_parquet/to_parquet -- as we are removing the proto format and this will become the default format for save/load_graph
• load_cached/write_updates/cache -- we have the WAL now

[jbaross-pometry]

Plan looks good to me, should simplify things a lot.

Some loose thoughts:

• filepaths: are these just any path relative to pwd of the python file or do we want e.g. a standrard /data dir that gets checked first with just filenames
• What do we need for the v4 switchover in file formats to make that smooth. We can recomend exporting using to_parquet before upgrading but it would be nice to have a dedicated conversion tool

[ljeub-pometry]

For the migration, the easiest would be for us to support reading the old proto format from v4 in load_graph such that you can just read your old graph and save it to the new format.

File paths will be relative to the current working directory or absolute paths. Same as any other file paths in python really.