chore: Add some HTTP outcalls metrics

[eichhorl]

Some metrics and logs for HTTPS outcalls:

• Add a label to the metric counting delivered flexible errors
• Add error and informational metrics to the pool manager
• Add a detailed log whenever a timeout is included in a block
• Track whenever the payload reaches the responses per payload limit (500)

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to cdc1354.

Security Overview

• 🔎 Scanned files: 9 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/repositories/f5e9d2bb-29a4-4b64-902a-391d65fd8b2d?scanId=9d1ea44a-f1b7-44dc-b4a2-330a5284783e&codeScanTypes=PrScan&tab=issues

Detected Code Changes

Change Type

Relevant files

Enhancement

► rs/consensus/src/consensus/metrics.rs     Change canister_http_flexible_errors_delivered from IntCounter to IntCounterVec and add labeling by type ► rs/https_outcalls/consensus/src/metrics.rs     Add IntCounterVec metrics for pool_manager_events and pool_manager_errors with type labels, and constants for label type ► rs/https_outcalls/consensus/src/payload_builder.rs     Introduce grouping of flexible_errors by kind using BTreeMap, and track new per-kind errors ► rs/types/types/src/batch/canister_http.rs     Add kind() method to map FlexibleCanisterHttpError variants to string labels for metrics ► rs/https_outcalls/consensus/src/payload_builder.rs     Update logic to increment new per-kind error counts when constructing consensus responses ► rs/https_outcalls/consensus/src/pool_manager.rs     Add metrics emissions on various failure paths (boundary node lookup, socks proxy resolution, committee lookup, signing, etc.) and events (requests sent, responses received, etc.) ► rs/https_outcalls/consensus/src/pool_manager.rs     Record additional pool manager events and error scenarios via metrics observations ► rs/https_outcalls/consensus/BUILD.bazel     Include ic-test-utilities-metrics in test utilities dependencies ► rs/https_outcalls/consensus/Cargo.toml     Add ic-test-utilities-metrics as a dependency ► rs/consensus/src/consensus/metrics.rs     Adjust construction of canister_http_flexible_errors_delivered to be a vector with type label ► rs/https_outcalls/consensus/src/payload_builder.rs     Add logging and metrics integration for timeout and per-kind error cases ► rs/https_outcalls/consensus/src/payload_builder.rs     Emit warning and metrics when max responses per block is reached ► rs/https_outcalls/consensus/src/payload_builder.rs     Record per-kind error counts and update tests to reflect BTreeMap-based stats