add comprehensive tests for serialization

Author: lukewilliamboswell

src/test.zig

@@ -6,6 +6,7 @@ test {
     testing.refAllDeclsRecursive(@import("builtins/main.zig"));
     testing.refAllDeclsRecursive(@import("cache.zig"));
     testing.refAllDeclsRecursive(@import("cache/mmap_cache.zig"));
+    testing.refAllDeclsRecursive(@import("test_serialization.zig"));
 
     // TODO: Remove after hooking up
     testing.refAllDeclsRecursive(@import("reporting.zig"));