refactor: Resolve JSCPD errors

[holtskinner]

Reduce copy/pasting detected by JSCPD

Clone found (python):
 - src/a2a/server/request_handlers/jsonrpc_handler.py [195:23 - 217:22] (22 lines, 124 tokens)
   src/a2a/server/request_handlers/jsonrpc_handler.py [121:23 - 143:15]

Clone found (python):
 - src/a2a/server/request_handlers/default_request_handler.py [256:9 - [27](https://github.com/google-a2a/a2a-python/actions/runs/15401445094/job/43334752070?pr=27#step:4:29)9:5] (23 lines, 179 tokens)
   src/a2a/server/request_handlers/default_request_handler.py [171:9 - 192:16]

Clone found (python):
 - src/a2a/server/request_handlers/default_request_handler.py [[28](https://github.com/google-a2a/a2a-python/actions/runs/15401445094/job/43334752070?pr=27#step:4:30)1:13 - [29](https://github.com/google-a2a/a2a-python/actions/runs/15401445094/job/43334752070?pr=27#step:4:31)1:6] (10 lines, 80 tokens)
   src/a2a/server/request_handlers/default_request_handler.py [191:17 - 201:70]

Clone found (python):
 - src/a2a/server/request_handlers/default_request_handler.py [408:9 - 423:6] (15 lines, 125 tokens)
   src/a2a/server/request_handlers/default_request_handler.py [109:9 - 123:6]

Clone found (python):
 - src/a2a/server/agent_execution/request_context_builder.py [12:5 - 20:5] (8 lines, 96 tokens)
   src/a2a/server/agent_execution/simple_request_context_builder.py [20:5 - 28:14]

Clone found (python):
 - src/a2a/utils/telemetry.py [192:2 - 212:7] (20 lines, 1[33](https://github.com/google-a2a/a2a-python/actions/runs/15401445094/job/43334752070?pr=27#step:4:35) tokens)
   src/a2a/utils/telemetry.py [158:2 - 178:11]

[swapydapy]

Not sure what is the need for two wrappers now, since they internally call the same function.

Maybe directly return the _invoke_with_tracing.

@rajeshvelicheti could you confirm.