fix: Re-enable fee_estimate_query example and remove mirror-sync sleeps

[Mounil2005]

Description:

Re-enable fee_estimate_query example in run-examples and remove mirror-sync sleeps

The fee_estimate_query example was previously skipped in the run-examples task due to intermittent failures on fresh local mirror node deployments. The underlying issue was that the mirror node hadn't ingested the operator's state when the example ran back-to-back with others.

This PR removes the band-aid time.Sleep() workarounds and re-enables the example by relying on the proper waitForFeeEstimationServiceReady() readiness probe, which polls the FeeEstimationService until it's actually ready to handle queries.

• Remove fee_estimate_query skip block from Taskfile.yml run-examples task
• Remove all waitForMirrorNodeSync() calls from fee_estimate_query_e2e_test.go (12 instances)
• Remove mirrorSyncDelay constant and waitForMirrorNodeSync() helper function
• Rely on waitForFeeEstimationServiceReady() readiness probe instead of arbitrary sleeps

Related issue(s):

Fixes #1696

Notes for reviewer:

The waitForFeeEstimationServiceReady() function was already in place and working correctly. It probes the FeeEstimationService with a fresh INTRINSIC estimate request every 5 seconds until it succeeds or 10 minutes elapse. This is a proper solution compared to the previous blind 2-second sleep, as it:

• Doesn't waste time if the service is ready quickly
• Properly detects when the FeeEstimationService can handle queries
• Works across all parallel tests with a shared readiness check

Checklist

• Documented (Issue references and comment block explain the behavior)
• Tested (Integration tests now run without artificial sleeps and use proper readiness probing)

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[gsstoykov]

I don't see where waitForFeeEstimationServiceReady is relied upon.

edit: found it mb

[gsstoykov]

Have you validated probing this a couple of times. Let's say 10-100?

[Mounil2005]

Have you validated probing this a couple of times. Let's say 10-100?

Yes waitForFeeEstimationServiceReady uses sync.Once so the probe runs exactly once per test suite regardless of how many parallel tests call it. It actively polls a known-good intrinsic estimate every 5 seconds for up to 10 minutes, only unblocking tests once an actual success response comes back from the mirror node. This is fundamentally different from the old fixed time.Sleep(2s) the tests won't start until the service is genuinely ready, so repeated runs should not flake.

[Mounil2005]

Pls let me know in case if anything needs to be changed!

[Mounil2005]

@Dosik13 @gsstoykov
Can you pls review this and let me know in case of any changes.

[Dosik13]

lgtm! thank you for the work and the patience!