feat(query): add table function udf_echo && expose more metrics of udf client

[sundy-li]

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Summary

feat: add udf_echo table function && expose more metrics of udf client

after databendlabs/databend-udf#11

1. udf_echo table function

example:

select * from udf_echo('http://m1:8815', 'abc');
┌────────┐
│ result │
│ String │
├────────┤
│ abc    │
└────────┘

2. add more metrics of udf client, now udf client has metrics as below.

| external_requests_total                 | counter   | {"function_name":"wait"}  |
│ external_running_requests_total  │ counter   │ {"function_name":"wait"}  |

│ external_connect_duration_sum     │ untyped    │ {"function_name":"wait"}  |
│ external_connect_duration_count   │ untyped    │ {"function_name":"wait"}  |
│ external_connect_duration_bucket │ histogram │ {"function_name":"wait"}  |

│ external_request_duration_sum    │ untyped   │ {"function_name":"wait"}  |
│ external_request_duration_count  │ untyped   │ {"function_name":"wait"}  |
│ external_request_duration_bucket │ histogram │ {"function_name":"wait"}  |

│ external_retry_total             │ counter   │ {"function_name":"wait","error_kind":"ConnectError"} │
│ external_error_total             │ counter   │ {"function_name":"wait","error_kind":"ConnectError"} │

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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This change is 

[flaneur2020]

LGTM 👍