Governance: Update addin accounts discriminators to Anchor compatible

[SebastianBor]

Summary

MaxVoterWeightRecord and VoterWeightRecord are defined in spl-governance-addin-api but they are owned by the addin programs. In order to make them easier to use in Anchor based programs their discriminators were updated to match the ones automatically generated by Anchor.

For backward compatibility with existing addins the legacy discriminator are also considered as valid ones.

[ckamm]

When I looked at this last time, the attempt to be compatible with Anchor didn't work because the discriminator field was part of the struct itself in spl-gov, while it's implicit for Anchor accounts structs. That was the reason the struct still needed to be wrapped (and we never ended up testing the account discriminator value). Wrapping code: https://github.com/blockworks-foundation/voter-stake-registry/blob/master/programs/voter-stake-registry/src/governance.rs

How do you use the struct with anchor without wrapping it?

[SebastianBor]

How do you use the struct with anchor without wrapping it?

I redefine the structs in Anchor program without the discriminator.
This way they are also automatically exported to the IDL without any workarounds