Move native level setups into level files

- Delete NativeLevelFixtures.kt and make native repository setup an optional property of each Level.
- Move every existing native setup into its corresponding level file so setup, validation, and tests stay together.
- Add the missing Blame native setup with config.rb history and a Spider Man password commit.
- Add a native runtime regression that verifies `git blame config.rb` identifies Spider Man on the password line.
- Verify the full JVM test suite using the compiled host Git runtime.

app/src/main/java/solutions/tretter/githugandroid/levels/MergeLevel.kt

@@ -14,6 +14,16 @@ internal fun mergeLevel(): Level = level(
     hints = listOf("You want to research the `git merge` command."),
     commandSuggestions = listOf("git merge feature"),
     setup = { RepoState(initialized = true, files = listOf(GitFile("file1", tracked = true)), branches = mapOf("master" to 1, "feature" to 2)) },
+    nativeSetup = {
+        resetFiles()
+        write("file1")
+        addCommit("added file1", "file1")
+        checkoutNew("feature")
+        write("file2")
+        addCommit("added file2", "file2")
+        checkout("master")
+        true
+    },
     validator = repoPredicate { repo -> repo.files.any { it.name == "file2" && it.tracked } },
     testCases = listOf(
         levelTestCase("merge feature", "git merge feature"),