Revert: Improve MSBuild SDK resolver by parsing global.json with System.Runtime.Serialization.Json #3157

[jeffkl]

Bug

Fixes: NuGet/Home#9098
Regression: Yes

• Last working version:
• How are we preventing it in future:

Fix

Details: Reverted #3157 and added unit tests to make sure this doesn't regress again.

Testing/Validation

Tests Added: Yes
Reason for not adding tests:
Validation:

[dtivel]

Thanks for adding tests. That's great.

Don't forget to update the PR title to accurately reflect the PR's intent.

[nkolev92]

You can consider keeping your test environment changes :)
Specifically your tests could still be using NuGet's infra.

[jeffkl]

You can consider keeping your test environment changes

I will send a follow up PR to remove the TestEnvironment class as a separate commit to expedite getting this in the next build.

[nkolev92]

Sounds good.
Feel free to merge when green, but Monday is also fine afaik.