Rename native code coverage paths product variables in Soong.

Rename `CoveragePath` and `CoverageExcludePaths` as
`NativeCoveragePath` and `NativeCoverageExcludePaths` (resp.).
Also rename function `android.CoverageEnabledForPath` as
`android.NativeCoverageEnabledForPath`.

Test: m nothing
Bug: 158212027
Change-Id: Id2c11a638e88088096420b537effa866d7667304
diff --git a/android/variable.go b/android/variable.go
index 3c08405..796aada 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -266,11 +266,11 @@
 
 	SamplingPGO *bool `json:",omitempty"`
 
-	NativeLineCoverage   *bool    `json:",omitempty"`
-	Native_coverage      *bool    `json:",omitempty"`
-	ClangCoverage        *bool    `json:",omitempty"`
-	CoveragePaths        []string `json:",omitempty"`
-	CoverageExcludePaths []string `json:",omitempty"`
+	NativeLineCoverage         *bool    `json:",omitempty"`
+	Native_coverage            *bool    `json:",omitempty"`
+	ClangCoverage              *bool    `json:",omitempty"`
+	NativeCoveragePaths        []string `json:",omitempty"`
+	NativeCoverageExcludePaths []string `json:",omitempty"`
 
 	DevicePrefer32BitApps        *bool `json:",omitempty"`
 	DevicePrefer32BitExecutables *bool `json:",omitempty"`