feat(GMX): add MegaETH chain support for events #2

[AIDataMaster]

Thank you for contributing to Spellbook 🪄

Please open the PR in draft and mark as ready when you want to request a review.

Description:

This PR introduces the initial GMX v2 event models for the MegaETH chain, focusing on core order events only.

Key Changes:

• Added MegaETH-specific event SQL models for:
  • gmx_v2_megaeth_order_created
  • gmx_v2_megaeth_order_executed
  • gmx_v2_megaeth_order_cancelled
  • gmx_v2_megaeth_order_updated
  • gmx_v2_megaeth_order_frozen
• Updated the chains loop in all relevant multi-chain gmx_v2_* models to include 'megaeth' where applicable.
• Staged additional MegaETH event models for future PRs to avoid Trino OUT_OF_SPILL_SPACE memory errors in CI.

(Note: This is Part 2 of the GMX v2 multichain expansion, intentionally limited to a small batch of 5 models to ensure CI stability. Additional MegaETH event models will be introduced in subsequent PRs.)

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quick links for more information:

• README.md
• spellbook docs
• CONTRIBUTING.md

[jeff-dude]

@AIDataMaster plz see #9646 and #9648
we needed to optimize models to avoid excessive compute in prod. the first PR was to start on simple market/glv created models, then when that worked, we scaled to rest of models which contained the join to raw transactions and cleaned up universally.
expectation is these megaeth PRs adapt to structure on main branch now.