commands: add `rbfpsbt` command #1508

Job	Run time
linter_gui	5m 44s
linter	35s
unit_tests (1.54, ubuntu-latest)	4m 55s
unit_tests (1.54, macOS-latest)	8m 2s
unit_tests (1.54, windows-latest)	6m 43s
unit_tests (nightly, ubuntu-latest)	51s
unit_tests (nightly, macOS-latest)	1m 32s
unit_tests (nightly, windows-latest)	1m 46s
unit_tests_gui (1.65, ubuntu-latest)	6m 28s
unit_tests_gui (1.65, macOS-latest)	13m 12s
unit_tests_gui (1.65, windows-latest)	8m 30s
unit_tests_gui (nightly, ubuntu-latest)	2m 32s
unit_tests_gui (nightly, macOS-latest)	2m 57s
unit_tests_gui (nightly, windows-latest)	4m 3s
	1h 7m 50s

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