Add support for obtaining default locale in Linux and fix issue with collation= not being passed to ICU

[steveharter]

(previously reviewed; moved from master to separate branch -- see #1704)

Fix for #3544 to enable default locale
Also fixed issue with @collection not being passed
Tests will be a PR in corefx soon

[dnfclas]

@steveharter, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, DNFBOT;

[bartonjs]

@steveharter A lot of corefx PRs are failing Linux tests for things like parsing integers, and this sounds suspiciously like it could have contributed.

Does this seem plausible to you?

cc: @stephentoub

[steveharter]

I ran System.Runtime.Tests.dll locally on Ubuntu with these change and all tests passed except for WaitHandleTests.WaitAllSameNames that threw System.PlatformNotSupportedException which seems unrelated (my environment or other issue). I will pull in later changes from others to see if I can get those parsing tests to fail.

[steveharter]

The tests were failing due to non-configured LANG setting on the test machines, which defaults to en-US-POSIX which has different default formatting than en-us or invariant. The tests were assuming invariant or equivalent compatible culture that formats numbers in a certain way.

The issue for now was addressed by defaulting en-us on the test machines.

Ideally the tests should explicitly use the invariant culture. Currently evaluating best way to address this