Split complex errors

Split the "Failed generating Proof of Membership" error message into 2 (https://github.com/Curve-Labs/lit-privacy/blob/main/packages/lit-privacy-sdk/src/LitPrivacy/LitPrivacy.ts#L145):
a. The user doesn't hold the token: Return the result of LA2.checkConditions to the SDK & check if the conditions are not met in the SDK, like this: https://developer.litprotocol.com/LitActions/workingWithActions/logAndReturn#returning-a-response
b. Other error (check params passed, etc)

Add error handling here

https://github.com/Curve-Labs/lit-privacy/blob/main/packages/lit-privacy-sdk/src/LitPrivacy/LitPrivacy.ts#L224