Linux plain text cache for headless linux

[siddharthpaudwal]

Made changes for azureauth code to work for headless linux machines
Token caching was not earlier available for headless machines and with this code changes, it will work

Tested the code changes in a linux machine and it is working -

[mvanchaa]

@siddharthpaudwal @kyle-rader had previously made related changes here #437 which can be merged unless this new PR is different :)

[siddharthpaudwal]

@siddharthpaudwal @kyle-rader had previously made related changes here #437 which can be merged unless this new PR is different :)

i have made few more changes in the PR, and we can merge this PR

[kyle-rader-msft]

We might want a way to disable the warning that gets printed to stderr via an env var to indicate. But otherwise, this is great.

[mijpeterson]

Approving with the caveat that the feedback items on here will be addressed ASAP.

[reillysiemens]

Approving with the caveat that most of the feedback items I've listed here should be addressed in some capacity, but especially the one about using MSAL APIs instead of our own permissions management. I expect to see that addressed in a follow-up ASAP.