[tests] Report errors last in RunApkTests (Take 2!)

[jonpryor]

Context: https://jenkins.mono-project.com/job/xamarin-android-pr-builder/2963/testReport/

A build for PR #1489 ran 1110 tests; it should have run over 35,000.
Where are the missing tests?

What's missing are the .apk on-device tests; BCL tests make up
most of our expected test count.

Analysis of the build log shows that the on-device tests are
running, with test results being downloaded:

…/android-toolchain/sdk/platform-tools/adb -s emulator-5570  pull "/data/data/Xamarin.Android.Bcl_Tests/files/.__override__/TestResults.xUnit.xml" "…/xamarin-android/tests/../bin/TestDebug/TestResult-Xamarin.Android.Bcl_Tests.xunit.xml"
...
/data/data/Xamarin.Android.Bcl_Tests/files/.__override__/TestResults.xUnit.xml: 1 file pulled. 53.5 MB/s (3273412 bytes in 0.058s)

but those results don't appear on the testReport URL.

The problem is that the RenameApkTestCases target is never being
executed, and the RenameApkTestCases is responsible for copying the
TestResult* files where Jenkins looks for them:

Done building target "ReleaseAndroidTarget" in project "RunApkTests.targets" -- FAILED.:

The RenameApkTestCases target executes after
ReleaseAndroidTarget, but because ReleaseAndroidTarget failed, the
RenameApkTestCases target isn't executed.

Meanwhile, ReleaseAndroidTarget reports an error to ensure that
errors aren't overlooked; see commit 3b893cd.

Allow the RenameApkTestCases target to execute by adding a new
ReportComponentFailures target. The ReleaseAndroidTarget will no
longer report errors, allowing the RenameApkTestCases target to
execute, while if any tests do fail, the ReportComponentFailures
target will generate an appropriate error.

Furthermore, update all the <MSBuild/> invocations within
RunTests.targets and add ContinueOnError="ErrorAndContinue" to all
of them, to help ensure that we run all the tests we have, even if
previous tests fail.

[jonpryor]

build