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/BranchAtLevel.kt

@@ -14,6 +14,16 @@ internal fun branchAtLevel(): Level = level(
     hints = listOf("Just like creating a branch, but you have to pass an extra argument."),
     commandSuggestions = listOf("git branch test_branch HEAD~1"),
     setup = { RepoState(initialized = true, commits = listOf(CommitNode("1", "Adding file1"), CommitNode("2", "Updating file1"), CommitNode("3", "Updating file1 again")), branches = mapOf("master" to 3)) },
+    nativeSetup = {
+        resetFiles()
+        write("file1")
+        addCommit("Adding file1", "file1")
+        write("file1", "content")
+        addCommit("Updating file1", "file1")
+        append("file1", "\nAdding some more text")
+        addCommit("Updating file1 again", "file1")
+        true
+    },
     validator = repoPredicate { repo -> repo.branches["test_branch"] == 2 },
     testCases = listOf(
         levelTestCase("branch at previous commit", "git branch test_branch HEAD~1"),