Fix up NetworkSecurityConfigTests.

* Outdated defaults for plain HTTP.
* Replaced expired test pins with the current intermediate.
issuer cert for android.com.
* Replaced obsolete trust anchors with a single GTS Root cert.
* Fixed connection tests to use startHandshake() not getInputStream().
* Made checkstyle happier.

Would have converted to JUnit4 too, but unsure how to
migrate ActivityUnitTestCase correctly.

Bug: 259406200
Test: NetworkSecurityConfigTests
Change-Id: I385fc4bb67cd937e9e5f7b291f2cee37fd9ad715