fix: race condition in conditional mock test

[EnriqueL8]

There was a race condition in the test on the way the consumers are added and we way for that , a cursor breakdown was useful

Timeline:
────────────────────────────────────────────────────────────────────
Test calls bl.addConsumer()
    │
    ├─► checkAndStartListenerLoop() ─► starts listener goroutine
    │
    ├─► waitUntilStarted() ◄─── BLOCKS HERE
    │                               │
    │       ┌───────────────────────┘
    │       │   Listener goroutine runs:
    │       │     1. eth_blockNumber ✓
    │       │     2. eth_newBlockFilter ✓
    │       │     3. eth_getFilterChanges ← conditionalMockOnce checks consumers
    │       │                               len(bl.consumers) == 0 ❌
    │       │                               Returns EMPTY array!
    │       │     4. markStarted() ← unblocks waitUntilStarted
    │       └───────────────────────┐
    │                               │
    ├─► waitUntilStarted() returns ◄┘
    │
    └─► bl.consumers[id] = consumer  ← Consumer added TOO LATE!

Test waits on: bu := <-updates  ← Never receives anything, TIMEOUT!

[EnriqueL8]

The other way to fix this is by adding a dummy mRPC.On("CallRPC", mock.Anything, mock.Anything, "eth_getFilterChanges", mock.Anything).Return(nil).Once() infront