test(role_store): cover revoke-side member-count and enumeration bookkeeping (#564)

[trakshan-mishra]

Description

Closes #564 — adds revoke-side member-count/enumeration bookkeeping tests to role_store.

The test module thoroughly exercises the grant side (test_role_member_enumeration checks count/members after two grants; test_idempotent_grant checks double-grant is a no-op) but never the revoke side:

• No test checks get_role_member_count after a revoke
• No test checks get_role_members excludes the revoked account
• No test exercises idempotent revoke
• No test revokes from a multi-member role to verify vec_remove_addr removes only the target

What changed

Added three tests mirroring the grant-side coverage:

1. test_revoke_decrements_count_and_removes_from_members — grant to two accounts, revoke one, assert count decremented by exactly one and get_role_members contains the remaining account but not the revoked one.

2. test_revoke_from_multi_member_preserves_others — grant to three accounts, revoke the middle one, assert the other two are still present (catches vec_remove_addr removing the wrong entry from a multi-member list).

3. test_idempotent_revoke — revoke twice, assert the count does not go negative or decrement twice (mirror of test_idempotent_grant).

Also adds a vec_contains_addr test helper (the existing vec_contains_b32 only works for BytesN<32>, not Address).

Verification

cargo test -p role-store   # 14 passed, 0 failed
cargo clippy -p role-store --all-targets -- -D warnings  # 0 warnings

Related issues

Closes #564