Allow user definition of buffer files

[zain-sohail]

In reference to disucssion on #264, we want to allow the user to be able to define a parquet location even if they already defined a beamtime directory already. Currently not possible.

sed/sed/loader/flash/loader.py

Line 926 in cb8eded

df, df_timed = self.parquet_handler(data_parquet_dir, **kwds)

Also other such inconsistences can be discussed here.

I think important addition would be if we allow for this buffer file feature in the base loader. That way loaders can just use it if needed. Also save to parquet feature.

[zain-sohail]

Should be easily possible after #329. Have to see what changes have to be made

[zain-sohail]

Done in #329

sed/sed/loader/flash/loader.py

Line 269 in 7f9422c

parquet_dir: str | Path = None,

Also possible by changing

sed/sed/loader/flash/loader.py

Line 47 in 7f9422c

self.parquet_dir: str = None

before calling read_dataframe but SedProcessor wrapper won't allow that