Add initial support for NU5 to zebra

[yaahc]

Motivation

We want to add a NetworkUpgrade::NU5 network upgrade variant, and a network protocol version for NU5.

Solution

This change updates various enums and constants to include variants for NU5.

The code in this pull request has:

• Documentation Comments
• Unit Tests and Property Tests

Review

@teor2345

Related Issues

Closes #1797

Follow Up Work

Need to implement actual NU5 logic, currently we panic if NU5 code paths get executed.

[oxarbitrage]

Looks good to me.

[teor2345]

Approved with changes and suggestions

Here's what I checked:

• the consensus branch id matches the draft spec
• the external network protocol versions match the draft spec

Here's what I suggested:

• the specific change and ZIP for each unimplemented!()
• remove unimplemented!() where there is no suggested change

Here's what I committed:

• add NU5 to the protocol::version_consistent test ae76f99

This test change isn't required until we have a testnet or mainnet activation height for NU5, but we might as well do it now.

[teor2345]

Since my suggestions were trivial, I went ahead and committed them.

[teor2345]

@oxarbitrage or @yaahc, can you double-check that:

• Each instance of Canopy in the codebase has a corresponding NU5

Let's focus on wildcard matches and other code that the compiler doesn't automatically pick up.

[oxarbitrage]

Thank you for the last changes @teor2345 , looks a lot better.

[teor2345]

We need to double-check that each instance of Canopy in the codebase has a corresponding NU5.

• @teor2345
• @yaahc
• @oxarbitrage

Let's just make sure 2 of us have checked this.

[oxarbitrage]

We don't have an element for NU5 in MAINNET_ACTIVATION_HEIGHTS and TESTNET_ACTIVATION_HEIGHTS because we don't know the exact block for this upgrade yet. However, we can add a placeholder there with block height 10_000_000 or something like that(with a todo comment to change it). If we do this or if we don't i think we should open a ticket to add(or modify) the block height for NU5 when this info became available.

The rest looks good in regards to all the instances of Canopy(specially all matches) have a corresponding NU5.

[yaahc]

@oxarbitrage you beat me to it but I just made a commit adding some TODO comments to the file, and I'll go ahead and add this follow up task to the checklist in the original issue

[teor2345]

We don't have an element for NU5 in MAINNET_ACTIVATION_HEIGHTS and TESTNET_ACTIVATION_HEIGHTS because we don't know the exact block for this upgrade yet. However, we can add a placeholder there with block height 10_000_000 or something like that(with a todo comment to change it).

We want to avoid implementing incorrect consensus rules, because:

• some Zebra instances might not be upgraded, so they will have the wrong rules
• people will get confused when they read our code

Zebra should work if some network upgrades don't have an activation height. So we can just add it when it is decided.

[teor2345]

Looks great, let's merge!