Re-adding a member to a onchain privacy group doesn't work

[lucassaldanha]

Description

When adding a member to an onchain privacy a second time, the rehydration doesn't happen and the member ends up out of sync with the privacy group.

Acceptance Criteria

• A member can be added and removed multiple times from an onchain privacy group
  • A member can always use priv_call at any block of the group and latest (we need a consistent PrivacyGHroupHeadBlock mapping)

Steps to Reproduce (Bug)

1. Create an onchain privacy group with member A
2. Send a private tx to the private group
3. Add member B to the privacy group (rehydration happens, B is in sync with the group)
4. Remove B from the privacy group
5. Send another private tx to the group
6. Add B to the privacy group again (rehydration DOES NOT happen, B is out of sync with the group)

Expected behavior: A member added to a privacy group is always on sync with the privacy group

Actual behavior: A member added to a privacy group a second time ends up out of sync with the privacy group

Frequency: Always

Versions (Add all that apply)

• Besu 1.4.1
• Orion 1.5.0