feat: clarify call responses configurations

[lwshang]

Description

All inter-canister calls are inherently best-effort operations. The key distinction in the System API ic0.call_with_best_effort_response is how long to wait for a response: either unboundedly or with a specified timeout.

By default, Call waits unboundedly for responses, as this is the only safe default behavior. In cases where bounded response time is safe (no significant cycles attached, no state change, idempotent endpoint, etc) developers can opt-in to timeout behavior using either with_timeout() for a default 10-second timeout or with_timeout_secs(...) for a custom timeout.

How Has This Been Tested?

Existing e2e-tests : call.rs got updated.

Checklist:

• The title of this PR complies with Conventional Commits.
• I have edited the CHANGELOG accordingly.
• I have made corresponding changes to the documentation.