XCTest integration in Xcode use the same build configuration as other targets

Tulsi use `__TulsiTestRunner_[Debug|Release]` as the build configuration in Xcode to silence the opinionated build process from Xcode and use Bazel build tool to do the automation. We settled on the same tactic for Gradle. However, the general feeling is we shouldn't need this workaround. More research needs to take place to ensure we aren't missing some other Xcode limitation.

### Expected Behavior
XCTest builds in Xcode use the same build configuration as all other targets removing the needs for `__GradleTestRunner_Debug` build configuration.

### Test Cases
- [ ] XCTest targets configure `Debug` build configuration
- [ ] The presence of XCTest target doesn't create `__GradleTestRunner_*` build configuration

Start by researching how XCTest targets select build configurations in Xcode and compare that behavior with the existing Gradle workaround described in the issue. Verify whether XCTest targets can use Debug without creating __GradleTestRunner_* configurations, then check both listed test cases.

Written by the indexing model from the issue text.