Python: Handle RPC deserialization errors in PythonRewriteRpc#parseProject()

[knutwannheden]

Summary

• Catch exceptions from getObject() in PythonRewriteRpc.parseProject()'s Spliterator and emit a ParseError instead of aborting the entire parse stream
• Add sourcePath to ParseProjectResponse.Item (both Python and Java sides) so the ParseError identifies which file failed
• Matches the existing error-handling pattern in RewriteRpc.parse()

Context

When an RPC deserialization error occurs (e.g., UnsupportedOperationException: Unknown state type END_OF_OBJECT), the exception propagated uncaught from tryAdvance() and killed the entire project parse operation. With this fix, the failing source file is represented as a ParseError and parsing continues with the remaining files.