[CCIP-12469] fix(commit): make observations non-blocking on stuck ops

[makramkd]

Problem

The commit plugin's chainfee.Observation was hanging indefinitely in production. Root cause: asynclib.WaitForAllNoErrOperations fans its operations out into goroutines and ends with an unconditional wg.Wait(). Despite setting a timeout on the context, however, it was not being honored by the LOOPP code because other callers are calling with an unbounded context (CCIP launcher here: https://smartcontract-it.atlassian.net/browse/CCIP-12413 already fixed, but headreporter has the same issue, still not fixed https://smartcontract-it.atlassian.net/browse/CCIP-12468) which caused the plugin caller to wait on a Lock() that would never get unlocked.

Solution

Replace the free function with a stateful asynclib.Runner:

• Time-bounded barrier. WaitForAll waits for completions or the timeout, whichever comes first, and proceeds with what finished. A stuck operation can no longer hold the round hostage.
• In-flight guard. An operation whose previous invocation is still running is skipped, not re-spawned. Goroutines are bounded to the number of distinct operations rather than accumulating one stuck goroutine per round.
• Empty, never stale. Results are per-round; a missing operation degrades to its zero value, and a late result from an abandoned goroutine is discarded. We prefer a visible missing price (which alerts) over silently posting a stale one.

Both commit observers (chainfee, tokenprice) now run through a reused Runner. This is defense-in-depth at the plugin boundary: the plugin can no longer be blocked by any downstream that ignores its context, independent of the chainlink-common connection fix and the launcher timeout fix in the companion PRs.

Testing

• New unit tests: an operation that ignores its context still lets WaitForAll return within the timeout; a stuck operation is not re-spawned on the next round.
• Existing chainfee/tokenprice unit + e2e tests pass; configs that relied on the old "ignore the timeout and wait forever" behavior now set an explicit per-round timeout (production applies this via ApplyDefaultsAndValidate).

[github-actions]

Metric	mk/unblock-chainfee	main
Coverage	69.7%	69.4%

[makramkd]

Verified on staging - commit plugin no longer blocks on a misconfigured Sui plugin.