tests(dot/core): Add tests against latest `gssmr` runtime

[timwu20]

Issue summary

• The following tests have been updated in PR fix(ci): embed old gssmr and dev runtimes for integration tests #2671 to point to the old gssmr runtime:
  • TestMaintainTransactionPool_EmptyBlock
  • TestMaintainTransactionPool_BlockWithExtrinsics
• Investigate and add new tests against latest gssmr runtime

Other information and links

• fix(ci): embed old gssmr and dev runtimes for integration tests #2671