test: Improve Test Coverage for packages/web3/src/block #452

[ShantelPeters]

Additional tests

1. BlockSubscription class (main implementation):

   • Testing the polling mechanism with different time intervals
   • Cache management and expiration
   • Handling of multiple chains in block responses
   • Error handling during polling
   • Missing blocks detection and handling

2. BlockSubscriptionBase class:

   • Edge cases for undefined reorgCallback
   • Handling of invalid block structures
   • Parent hash calculation with edge cases

3. Key scenarios that should be tested:

   • Timestamp handling (future timestamps, expired timestamps)
   • Network errors and retry behavior
   • Block ordering and sorting
   • Chain reorganization with various depths
   • Cache management with concurrent updates

Resolves #452