feat: reorganize project

[lekhovitsky]

This commit focuses on improving project structure.

First of all, core-v2 references are finally removed.

Next, governance/ directory is dissected:

• gauge and rate keeper are moved into pool/
• staking is moved into core/
• controller timelock is moved into governance repo

[github-actions[bot]]

:tada: This PR is included in version 1.50.0-next.8 :tada:

The release is available on:

• npm package (@next dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: