chore: add testing framework

[joepegler]

PR-Codex overview

This PR focuses on enhancing the testing framework for blockchain interactions, integrating environment variable configurations, and improving support for paid transaction testing. It also includes updates to type definitions, utility functions, and workflow configurations.

Detailed summary

• Deleted src/tests/e2e.test.ts.env.example.
• Updated tsconfig.json to include tests.
• Modified GitHub Actions workflows for installing dependencies and running tests.
• Introduced environment variables for test configurations.
• Added networkTest and setup utilities in tests/setup.ts and tests/globalSetup.ts.
• Updated src/account-vendors/nexus/multichain-nexus.account.ts to use Chain[] instead of NonEmptyArray<Chain>.
• Created new GitHub Actions workflow for paid tests.
• Implemented getExplorerTxLink function in src/utils/explorer/explorer.ts.
• Added Vitest configuration in tests/vitest.config.ts for coverage reporting.
• Updated src/mee.service.ts warning messages.
• Enhanced README.md with test setup instructions and prerequisites.
• Refactored payGasWith function in src/utils/syntax/supertransaction-builder.util.ts.
• Added unit tests in src/utils/explorer/explorer.test.ts and src/account-vendors/account.test.ts.
• Expanded tests/README.md with detailed testing framework documentation.
• Implemented network initialization logic in tests/config.ts.

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[github-actions]

size-limit report 📦

Path	Size
core (esm)	10.77 KB (-0.77% 🔽)
core (cjs)	13.06 KB (-0.97% 🔽)