feat(rln): implement a _light_ non-zerokit version for registrations/credentials management

[danisharora099]

Description

For RLN, and credentials management, we were relying on RLN instance, which internally relies (and loads) Zerokit.
This Zerokit WASM blob takes about 15 seconds in the browser to load.

With work on the KeyStore Management application, which strictly requires credentials management and no RLN proof generation/verification (where Zerokit becomes necessary), we realise that Zerokit can be eliminated for this process.

User Story

• User should be able to register a membership without Zerokit
• User should be able to generate/delete/manage credentials without Zerokit

Proposed Solution / Feature Design

• Use local hashing instead of relying on Zerokit

Notes

[danisharora099]

• webapp: feat(keystore-management): provide RLNLight implementation, without Zerokit, for credentials generation (registration) lab.waku.org#116
• js-waku: feat(rln): create CredentialsManager without Zerokit #2295