feat(rln): improve validation of whether membership can be erased

[adklempner]

Description

The function used to submit a transaction that erases a membership:

1. Uses 2 RPC requests to check conditions that can be handled with a multicall, or by checking the custom error when simulating the transaction
2. Doesn't support the case where the caller is also the owner of a membership and wants to erase it during the grace period.

User Story

Proposed Solution / Feature Design

Optional: Diagram or Draft of Design

Notes