Utilize echopype working directory

[lsetiawan]

Overview

After the acceptance of the idea for an echopype working directory, the team have decided to do the following after PR #896 is merged:

• move all the temp directories and temp zarr files into this hidden directory, instead of the current temp_echopype_output directory
• move all the testing framework and files into this hidden directory

Originally posted by @leewujung in #896 (comment)

[leewujung]

A note that I was just looking at what combine_echodata does -- seems that if no destination path is given, the combined file will get saved at temp_echopype_output/combined_echodatas.zarr (see here).

I have two complaints:
1 . echodataS doesn't make sense to me -- how about just combined _echodata.zarr?
2. currently in io.validate_output_path, the way docstring is written it is not clear that whatever in source_file is ignored if save_path is a full path (including filename) and not just a path to a folder:

echopype/echopype/utils/io.py

Lines 214 to 230 in e73fa14

	if is_dir:
	check_file_permissions(sanitized_path)
	out_path = os.path.join(save_path, Path(source_file).stem + file_ext)
	else:
	if isinstance(sanitized_path, Path):
	check_file_permissions(sanitized_path.parent)
	final_path = sanitized_path
	out_path = str(final_path.parent.joinpath(final_path.stem + file_ext).absolute())
	else:
	path_dir = fsspec.get_mapper(os.path.dirname(save_path), **output_storage_options)
	check_file_permissions(path_dir)
	final_path = Path(save_path)
	out_path = save_path
	if final_path.suffix != file_ext:
	logger.warning(
	"Mismatch between specified engine and save_path found; forcing output format to engine." # noqa
	)

@lsetiawan : what do you think about making these changes as you work on this issue to use the hidden default directory? For 2. it could just a docstring change for clarification, but it feels a little bizarre to have source_file and save_path partially overlap only sometimes. Thoughts? (I am fine with keeping it as is to not disturb anything major, but thought we should discuss regardless.)

[leewujung]

This is addressed in #954.