Dynamic dust limit

[luke-jr]

There is now (as of 26.1) experimental (and disabled by default) support for dynamically adjusting the "dust" spam filter threshold. It can be enabled in the GUI, or by configuring -dustdynamic=target:N to adjust based on a fee estimate for confirmation within N blocks, or -dustdynamic=mempool:N to adjust based on the worst fee in the best N kvB of your mempool. In either mode, the fee will be adjusted every 15 minutes (the first time not for 15 minutes after startup, in an effort to ensure estimators have sufficient data to work with). Implementation details (including how often adjustment occurs) may be changed in future releases.

Please comment here if you have tested this feature, your experiences with it, and/or any other suggestions.