Make the Installation of S3 Optional in Release Packages

[NivekT]

🚀 The feature

Make the installation of S3 optional in release packages.

Motivation, pitch

It will make our library a pure Python package, which will be easier to install.

Alternatives

Keep things as they are.

Additional context

cc: @ejguan

[ejguan]

I have two concerns:

• Domain teams have experienced some users' complaint about the installed packages are the legacy versions. This is caused new binaries (with C++ code) has not provided the binary for a specific OS/Arch like M1, then it will automatically fallback to the previous package that is in pure python.
• We are kind making a BC breaking change for binary distribution

I would support to add a pure python package to both pypi and conda, if it's possible, which won't block us to still provide OS-specific binary. I users couldn't use the OS-specific one, they can still fallback to install python package directly.