Refactoring tasks for v-next

[schaable]

Here's a list of refactoring tasks we can work on to improve consistency and clarity:

• [x] ~~v-next/core/src/global-dir.ts: Path is too high in the hierarchy. It should be moved to v-next/core/src/internal or v-next/core/src/internal/utils.~~ Moved to hardhat-utils/global-dir.
• [ ] v-next/hardhat/src/internal/constants.ts and v-next/hardhat/src/internal/cli/init/constants.ts should be unified.
• [ ] v-next/hardhat/src/internal/cli/helpers/getGlobalHelpString.ts and v-next/hardhat/src/internal/cli/helpers/getHelpString.ts should be renamed to snake-case.
• [ ] The path v-next/hardhat/src/internal/cli/helpers contains files related to the help CLI option, but the name could be more explicit. Renaming it to help would be consistent with the init folder and avoid confusion with utils folders.
• [x] v-next/hardhat/src/internal/helpers/config-loading.ts should be moved to v-next/hardhat/src/internal or v-next/hardhat/src/internal/utils.