change(consensus): Allow configurable NU5 activation height on Regtest

[arya2]

Motivation

We want to allow configuring an NU5 activation height on Regtest. This was removed in a recent PR because I thought Zebra didn't support Canopy block construction, it does, it was the proposal_block_from_template() function used in tests and the internal-miner that only worked with NU5.

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Solution

• Accept a current_network_upgrade argument in proposal_block_from_template()
• Select which field from the template should be used in the block based on the current network upgrade
• Use the testnet_parameters.activation_heights.nu5 field as the NU5 activation height on Regtest

Related Changes:

• Updates with_activation_heights() to overwrite activation heights for all network upgrades except Genesis
• Adds current_with_activation_height() method and uses it in Commitment::from_bytes()

Testing

The regtest_submit_blocks() test was updated to submit Canopy blocks and switch to NU5 blocks at height 100

Review

Anyone can review.

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[oxarbitrage]

looks good to me, thanks!