fix: Update time of HTTP outcalls contexts when moving them to delivered

[eichhorl]

HTTP outcalls contexts are moved to a different delivered collection, as soon as the response is delivered. There, they wait for further asynchronous refunds to be delivered. Previously, the context would be removed from this collection after a timeout of 2 minutes, since the creation of the original context.

With this PR, we instead update the context's time when moving it to delivered, and remove it after a timeout of 1 minutes, since the insertion into delivered contexts. This reduces the amount of time that the context needs to stay in replicated state.

Additionally, we add metrics for the amount of cycles being refunded. We observe the total amount, and its fraction against the per-replica allowances.

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to 3ea40bf.

Security Overview

• 🔎 Scanned files: 4 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/repositories/f5e9d2bb-29a4-4b64-902a-391d65fd8b2d?scanId=2e2a9453-e171-43fc-9216-8fd2a2bcddde&codeScanTypes=PrScan&tab=issues

Detected Code Changes

Change Type	Relevant files
Enhancement	► rs/execution_environment/src/execution_environment.rs        Use updated context retrieval with current time for subnet call context manager
Enhancement	► rs/messaging/src/canister_http_spent.rs        Add refund tracking metrics: refunded_cycles and refunded_fraction        Introduce status labeling (complete/incomplete) for refunds        Initialize and observe refund metrics        Record refunds upon context drop
Enhancement	► rs/replicated_state/src/metadata_state/subnet_call_context_manager.rs        Change DELIVERED_CANISTER_HTTP_REQUEST_CONTEXT_TIMEOUT to 60 seconds        Extend retrieve_context to accept current_time and stamp delivered contexts with it        Update time_out_delivered_canister_http_request_contexts documentation to reflect new timing semantics
Enhancement	► rs/replicated_state/src/metadata_state/tests.rs        Update tests to pass time parameter to retrieve_context calls
Enhancement	► rs/replicated_state/src/metadata_state/tests.rs Adjust tests for new delivered context time stamping and timeout behavior in canister HTTP context retrieval and timeouts