Description

This pull request removes support for legacy modules smart contracts from the codebase and integration tests. This includes deleting all related source code, configuration, and build logic for legacy contracts, and updating integration test dependencies to only use the current modules. The goal is to clean up deprecated functionality and prepare for future upgrades.

Removal of legacy modules smart contracts:

• Deleted the entire integration-tests/contracts/legacy-modules directory, including all Rust contract code, configuration files, and documentation.

• Removed the WasmLegacyModulesDir constant and all references to legacy modules in build/tx-chain/wasm.go.
  Integration tests cleanup:

• Updated integration test dependency lists to remove compilation and usage of legacy modules smart contracts in build/tx-chain/tests.go.

Preparation for future upgrades:

• Added TODO comments in app/app.go to indicate future removal of legacy message and query handlers.

Reviewers checklist:

• Try to write more meaningful comments with clear actions to be taken.
• Nit-picking should be unblocking. Focus on core issues.

Authors checklist

• Provide a concise and meaningful description
• Review the code yourself first, before making the PR.
• Annotate your PR in places that require explanation.
• Think and try to split the PR to smaller PR if it is big.