Remove Orchestrator's single method fast path

[PhilGlass]

Overview

Fixes #2132.

Orchestrator has a fast path that skips test discovery if the test target is a single method. This doesn't work for parameterized tests, since even a single method target may expand to any number of parameterized test instances.

Proposed Changes

Remove the fast path and always run test discovery, because I don't think it's possible to know ahead of time whether a test target expands to exactly 1 test.

Tested locally by running:

bazelisk build :axt_m2repository
unzip bazel-bin/axt_m2repository.zip -d ~/.m2/

and running one of the parameterised tests in our repo against the 1.5.0-alpha03 orchestrator artifacts in ~/.m2 (mavenLocal() in Gradle build scripts).