[dependency] Update halo2 version to latest `main` for the entire workspace

[CPerezz]

Currently the workspace is using:

[patch.crates-io]
halo2 = { git = "https://github.com/appliedzkp/halo2.git", rev = "b78c39cacc1c79d287032f1b5f94beb661b3fb42" }

The idea is to simply use main at latest commit height. So:

[patch.crates-io]
halo2 = { git = "https://github.com/appliedzkp/halo2.git", rev = "514152c8b83de27a5ce17ef70cc44c4092240bd1" }

[CPerezz]

This will help a lot for error debugging like in #331 or in #320 since the new version comes with AssignedCell type included

[barryWhiteHat]

4cf8ba3 might be a bunch of hte work for this. Ping @noctrlz

[CPerezz]

Thanks for catching this @barryWhiteHat !

It indeed contains everything AFAIS. Some stuff might not be precisely as needed (at least for keccak) but contains almost all.
What should I do? As the PR has been untouched for like 13 days.

Can I commit on the top of it to put the keccak stuff in order? Or what's the strategy?

[CPerezz]

After discussing with @noctrlz, We can ignore for now #302 as is just for benchmarks and also conflicting and proceed with a PR for the update.

[ashWhiteHat]

@CPerezz
I was successful for update halo2.
I hope this helps you.
#321

And following PR, I introduced latest kzg commitment scheme.
I changed the base main -> feat/halo2-update so you can check the diff.
#302

In terms of Cargo.toml dependencies, the assembly pairing was merged into pairing master and kzg-rebase also merged into halo2 master.
We don't have to indicate branch anymore.

[CPerezz]

Ye, I saw this!

I'm almost done. I think the rebase will be really easy! :)

I'm updating to current halo2 master. The idea would be that we release a tag for it which makes it easier for us to identify versions.