Make native_coverage clause work with ClangCoverage

Make uses NATIVE_COVERAGE to enable gcov coverage and CLANG_COVERAGE
to enable clang coverage.  NATIVE_COVERAGE is translated to the Soong
Native_coverage product variable which triggers the native_coverage
clause in Android.bp files.  The clause also needs to be triggered
for CLANG_COVERAGE.

Rename the existing Native_coverage product variable to GcovCoverage,
and regenerate Native_coverage when either GcovCoverage or
ClangCoverage are set.

Also remove NativeLineCoverage, it wasn't doing anything differently
than Native_coverage.

Bug: 159059537
Test: m checkbuild
Change-Id: I215124a9b35a2ad50ad562079d392e3d33da11f4
diff --git a/java/app.go b/java/app.go
index 4bb292d..1d2c582 100755
--- a/java/app.go
+++ b/java/app.go
@@ -938,7 +938,7 @@
 }
 
 func (a *AndroidApp) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
-	return ctx.Device() && (ctx.DeviceConfig().NativeCoverageEnabled() || ctx.DeviceConfig().ClangCoverageEnabled())
+	return ctx.Device() && ctx.DeviceConfig().NativeCoverageEnabled()
 }
 
 func (a *AndroidApp) PreventInstall() {