feat(r8-tests): Add R8 synthetic tests

[romtsn]

Part of #40

The tests are currently failing because we just mark methods as synthetic but don't drop them in this crate. Unsure if we should align with retrace and just drop them cc @loewenheim ?

R8 Retrace Test Coverage

• Inlining (13 tests) - inline frames, line numbers, source files, rewriteFrame rules
• Ambiguous Methods (21 tests) - multiple methods → same obfuscated name, alternatives
• Outlines (4 tests) - outline callsites, nested outlines, inline-in-outline
• Synthetic/Lambda (3 tests) - lambda methods, synthetic bridges
• Source File Edge Cases (7 tests) - colons, unicode, multiple dots, synthesized names
• Line Number Handling (10 tests) - spans, preambles, invalid ranges, missing lines
• Exception Handling (6 tests) - obfuscated exceptions, suppressed, circular refs
• Method Overloading (4 tests) - overloads with/without ranges
• Mapping Versions (2 tests) - version warnings, multiple versions
• Special Formats (4 tests) - Java 9+ modules, logcat format, auto-detect
• Identity/Passthrough (2 tests) - identity mappings
• Real-World Bot Tests (4 tests) - production stack traces
• Edge Cases (6 tests) - invalid input, dashes in names, whitespace, field overlap

[loewenheim]

We could filter them out in remap_stacktrace, yeah. For the remap_stacktrace_typed I would leave it as it is.