more precise types for signature type in confirmations

[mmv08]

This pull request to packages/types-kit includes changes to enhance type safety and consistency in the codebase. The most significant changes involve the introduction of a new SignatureTypes constant and the corresponding SignatureType type and modifying existing types to utilize these new definitions.

Enhancements to type safety and consistency:

• packages/types-kit/src/types.ts: Added SignatureTypes constant and SignatureType type for improved type safety.
• packages/types-kit/src/types.ts: Updated SafeMultisigConfirmationResponse to use the new SignatureType type instead of a string.

Reference to the SafeSignatureType enum in safe-eth-py and safe-transaction-service:

1. https://github.com/safe-global/safe-eth-py/blob/4eceab2160a72052f0a1d5efaa2af5d78f464371/safe_eth/safe/safe_signature.py#L40
2. https://github.com/safe-global/safe-transaction-service/blob/8fb64a47b024aecaebdf5968a56bb4df08959a91/safe_transaction_service/safe_messages/models.py#L71-L73

[mmv08]

regarding enum vs const enum vs const:
https://www.perplexity.ai/search/enum-vs-const-enum-in-typescri-bBwicw7YQDGRvdxEiM56zA#0

here's why I went with const:

Type safety
Runtime object availability
No extra generated code
Better compatibility with modern JavaScript practices6

https://www.typescriptlang.org/docs/handbook/enums.html#objects-vs-enums

[mmv08]

The tests failed because the private key was of the wrong size. I think it's because the PR is from a fork and it doesn't have access to environment variables