Joblib integration tests

[cosmicBboy]

TL;DR

Add more unit/integration tests for FlyteFile.

Type

• Bug Fix
• Feature
• Plugin
• Tests

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

This PR adds unit tests for the different FlyteFile type variants, as well as an integration test to make sure that the JoblibSerialized type can be correctly serialized/deserialized when used in a FlyteRemote.

Tracking Issue

NA

Follow-up issue

NA
OR
https://github.com/lyft/flyte/issues/

[codecov]

Codecov Report

Merging #677 (5dc66ca) into master (f6ee06f) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #677      +/-   ##
==========================================
+ Coverage   85.63%   85.65%   +0.01%     
==========================================
  Files         355      355              
  Lines       29650    29661      +11     
  Branches     2415     2415              
==========================================
+ Hits        25391    25406      +15     
+ Misses       3618     3615       -3     
+ Partials      641      640       -1     

Impacted Files	Coverage Δ
tests/flytekit/integration/remote/test_remote.py	91.62% <100.00%> (+0.51%)	⬆️
flytekit/types/file/file.py	90.84% <0.00%> (+2.81%)	⬆️

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