Refactor file handling to use 'with' statement

[allrob23]

Closes #9499

Change List

• Refactored the file handling in bindings/pydeck/tests/fixtures.py to use the with open() statement.

[felixpalmer]

There appear many other places in the python code that use open without with. I'm not against this change, but if you're going to fix it in one place, can you fix it in all files - so the usage is consistent?

[allrob23]

Ok. I will do that.

[allrob23]

I have updated all occurrences where open was used without with across all files to ensure consistency. Let me know if you need any further adjustments.

[allrob23]

Hey @felixpalmer, just following up to see if you might have a chance to review this.
Appreciate your time!

[coveralls]

coverage: 91.634%. remained the same
when pulling 7385ee0 on allrob23:master
into b1e4a9f on visgl:master.