Set the NU6 testnet activation height and network protocol version

[mpguerra]

Motivation

We need to update the consensus parameters for NU6 testnet.

Specifications

TBD: (We need to wait for the relevant NU6 deployment ZIP)

Complex Code or Requirements

No response

Testing

No response

Related Work

#4115
#8681
depends-on: zcash/zips#878
depends-on: zcash/librustzcash#1454

[oxarbitrage]

zcash/zips#878

[oxarbitrage]

This issue is straightforward to do but it is blocked by several reasons:

• The ZIP with the info we want to add is a draft: [ZIP 253] Initial draft zcash/zips#878
• zcash_primitives need to have Nu6 data: Make nu6 rust feature stable zcash/librustzcash#1454

Assuming we can have stable Nu6 in the next zcash_primitives release, we also need:

• Deal with the release breaking changes and upgrade Zebra before adding the constant values.

[arya2]

CURRENT_NETWORK_PROTOCOL_VERSION needs to be bumped to 170_110 too so that peer candidates won't reject Zebra after NU6 is active.

We also need to set the Testnet activation height, this issue was closed mistakenly.

[mpguerra]

this is now done