Testing Idena node: release candidate 0.26.6-rc1

[midenaio]

We invite you to test the release candidate version of the Idena node: 0.26.6-rc1.
Please download it manually if you'd like to join the testing.

Changes:

• Performance improvement: ~x4 speed up fast sync
• Performance improvement: postponed validation of blocks
• Performance improvement: disable noise protocol
• Adjust consensus engine timeouts
• Save mempool transactions on disk

We plan to release these changes in two days unless negative feedback is received.