remove python 3.4 support

[fengzhou-msft]

Fix #11391

[yungezz]

what's the whole plan of remove python 3.4 support, such as plan for users using 3.4 today

[fengzhou-msft]

what's the whole plan of remove python 3.4 support, such as plan for users using 3.4 today

Current azure-cli code already breaks with python 3.4, this is to remove python 3.4 from language support list.

[haroldrandom]

@fengzhou-msft Could you reference some issues or problems?

Offering a case, but not related to OpenSSL.
I test to install azure-cli in Ubuntu 18.04 under Python 3.4. Breaks by requests~2.22 not supported.

[yonzhan]

@fengzhou-msft Share we add Python 3.8 support in all setup.py recently?

[fengzhou-msft]

@fengzhou-msft Share we add Python 3.8 support in all setup.py recently?

We have done that for the main packages in last sprint. I added it in the remaining setup.py files in this PR.