Incorrect Ed25519VerificationKey publicKeyMultibase conversion

[DaevMithran]

Bug severity: 3

Describe the bug
Conversion of publicKeyMultibase to publicKeyHex in Ed25519VerificationKey2020 doesn't remove the Multibase header present in the publicKeyMultibase according to the spec

To Reproduce
Steps to reproduce the behaviour:

1. Issue a JsonLD credential using an assertion method of type Ed25519VerificationKey2020 in a Issuer DID. This will result in an error.

Observed behaviour
This is the below observed behviour, as the prefix is not removed the publicKeyHex is different from the local wallet keys

throw Error(`key_not_found: No suitable signing key found for ${identifier.did}`);
                  ^
Error: key_not_found: No suitable signing key found for did:cheqd:testnet:570996eb-393a-4659-8f88-71cb53488eb4
    at CredentialIssuerLD.findSigningKeyWithId 

Expected behaviour
The credential should be issued to the holder

2. Verify JWT credential issued by Ed25519VerificationKey2020 method Issuer DID.

Observed behaviour
The credential was not verified successfully

Expected behaviour
The credential was verified successfully