Add teleport debug metrics command

[wethreetrees]

Purpose

Adds a command to the teleport cli to query the /metrics endpoint to accommodate restricted environments, e.g. curl unavailable.

resolves #62175

Testing

1. Start Teleport

./build/teleport start --diag-addr=127.0.0.1:3001

2. Run metrics command and save output to file

./build/teleport debug metrics > metrics.txt

3. Compare command output with output from metrics endpoint

curl http://127.0.0.1:3001/metrics

Example output (truncated for brevity):

# HELP audit_failed_disk_monitoring Number of times disk monitoring failed.
# TYPE audit_failed_disk_monitoring counter
audit_failed_disk_monitoring 0
# HELP audit_failed_emit_events Number of times emitting audit event failed.
# TYPE audit_failed_emit_events counter
audit_failed_emit_events 0
# HELP audit_percentage_disk_space_used Percentage disk space used.
# TYPE audit_percentage_disk_space_used gauge
audit_percentage_disk_space_used 0
# HELP audit_server_open_files Number of open audit files
# TYPE audit_server_open_files gauge
audit_server_open_files 0
# HELP auth_generate_requests Number of current generate requests for server keys
# TYPE auth_generate_requests gauge
auth_generate_requests 0
# HELP auth_generate_requests_throttled_total Number of throttled requests to generate new server keys
# TYPE auth_generate_requests_throttled_total counter
auth_generate_requests_throttled_total 0
# HELP auth_generate_requests_total Number of requests to generate new server keys
# TYPE auth_generate_requests_total counter
auth_generate_requests_total 0
# HELP auth_generate_seconds Latency for generate requests for server keys
# TYPE auth_generate_seconds histogram
auth_generate_seconds_bucket{le="0.001"} 0
auth_generate_seconds_bucket{le="0.002"} 0
auth_generate_seconds_bucket{le="0.004"} 0
auth_generate_seconds_bucket{le="0.008"} 0
auth_generate_seconds_bucket{le="0.016"} 0
auth_generate_seconds_bucket{le="0.032"} 0
auth_generate_seconds_bucket{le="0.064"} 0
auth_generate_seconds_bucket{le="0.128"} 0
auth_generate_seconds_bucket{le="0.256"} 0
auth_generate_seconds_bucket{le="0.512"} 0
auth_generate_seconds_bucket{le="1.024"} 0
auth_generate_seconds_bucket{le="2.048"} 0
auth_generate_seconds_bucket{le="4.096"} 0
auth_generate_seconds_bucket{le="8.192"} 0
auth_generate_seconds_bucket{le="16.384"} 0
auth_generate_seconds_bucket{le="32.768"} 0
auth_generate_seconds_bucket{le="+Inf"} 0
auth_generate_seconds_sum 0
auth_generate_seconds_count 0
# HELP backend_batch_read_requests_total Number of read requests to the backend
# TYPE backend_batch_read_requests_total counter
backend_batch_read_requests_total{component="backend"} 31
# HELP backend_batch_read_seconds Latency for batch read operations
# TYPE backend_batch_read_seconds histogram
backend_batch_read_seconds_bucket{component="backend",le="0.001"} 31
backend_batch_read_seconds_bucket{component="backend",le="0.002"} 31
backend_batch_read_seconds_bucket{component="backend",le="0.004"} 31
...

changelog: Added teleport debug metrics command

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Branch	Result
branch/v18	Create PR