Convert recursion of mempool/removeOrphans (when removeRedeemers = true) to loop

[svarogg]

Currently orphans are limited to 100, but we might want to increase the number, thus we should remove the recursion, to avoid stack overflows.

When solving this - remove the comment above defaultMaximumOrphanTransactionCount saying

	// defaultMaximumOrphanTransactionCount should remain small as long as we have recursion in
	// removeOrphans when removeRedeemers = true