bdk_esplora redundantly stores height in its anchor

[LLFourn]

See:

bdk/crates/esplora/src/lib.rs

Lines 27 to 31 in 55b680c

	Some(ConfirmationTimeHeightAnchor {
	anchor_block: BlockId { height, hash },
	confirmation_height: height,
	confirmation_time: time,
	})

Esplora should have its own anchor which is BlockIdWithTime for example. It can still be defined in bdk_chain and shouldn't cause friction if the requisite From implementations are done for ConfirmationTimeHeightAnchor.