[py] Add high-level BiDi network response handler API

[AutomatedTester]

🔗 Related Issues

💥 What does this PR do?

Adds the doc-aligned high-level response interception API to driver.network (Phase 2 of the BiDi Protocol API Design, following #17619):

• add_response_handler(callback) / add_response_handler(url_patterns, callback) with the same glob URL patterns as request handlers (*, **, ?), plus remove_response_handler(handler_id) and clear_response_handlers()
• New Response object at the responseStarted intercept phase exposing url, status, reason_phrase, headers, mime_type, with set_status/set_headers/set_cookies/set_body mutators (BiDi does not expose the original body or parsed cookies at this phase, so those start empty)
• After all matching handlers run, the outcome is reconciled into exactly one BiDi command per response: a mutated body is delivered via network.provideResponse (carrying over the current status/headers), other mutations via network.continueResponse, untouched responses are continued unmodified — observer-only handlers never stall the page
• Graceful degradation: if the browser rejects provideResponse at this phase (Firefox only supports the body parameter at beforeRequestSent), the response is continued with the remaining mutations instead of leaving the page blocked

🔧 Implementation Notes

• The request/response registries now share a _BaseHandlerRegistry in py/private/_network_handlers.py parameterized by intercept phase, event key and wrapper class; RequestHandlerRegistry behavior is unchanged (all pre-existing unit tests pass unmodified)
• clear_request_handlers() (the legacy clear-everything sweep) now preserves response-handler intercepts and re-establishes the response registry's event subscription; clear_response_handlers() symmetrically only touches response handlers
• The response_started event is overridden in the enhancement manifest to deliver raw dict params — the same fix the manifest already applies to auth_required/before_request, because the generated ResponseStartedParameters dataclass only keeps response, dropping request, isBlocked and intercepts (without this, blocked responses were never continued and navigation hung)

🤖 AI assistance

• AI assisted (complete below)
  • Tool(s): Claude Code
  • What was generated: Response/registry refactor in _network_handlers.py, manifest glue, and tests, from the BiDi Protocol API Design doc
  • I reviewed all AI output and can explain the change

💡 Additional Considerations

• High-risk area: wire-level network interception semantics — the new reconciliation applies to the new-style response handlers only; request-handler and legacy paths are preserved
• Verified locally: 39/39 unit tests; live browser runs — Chrome 23 passed / 1 skipped, Firefox 22 passed / 2 xfailed (test_change_response_body xfails on Firefox with the provideResponse phase limitation)
• Remaining phases: callback-based authentication handlers with cancel(), extra-headers API, Script module alignment
• Cross-binding parity (Java/Ruby/JS) for the doc-aligned naming is follow-up work

🔄 Types of changes

• New feature (non-breaking change which adds functionality and tests!)