adding bankrun context wrapper

[heyAyushh]

• This BankrunContextWrapper wrapper is needed so that we can use connection object in anchor-bankrun or solana-bankrun
• refactored functions into logical files
• changed build steps to include cjs along with esm module
• introduced testing with ts-jest
• fixed type definitions not found

[mikemaccana]

This is a large PR with a lot of unrelated work. In general, use one PR for each change you're going to make - that way they can be reviewed, merged, and (if needed) reverted separately.

Please split this work into multiple PRs.

• The build changes to support CommonJS libraries
• Adding a bankrun helper
• Reorganizing the code into multiple files
• Ignoring node's test runner for ts-jest - we want to avoid adding unnecessary dependencies, so in whatever PR you made that adds ts-jest, state why you're adding it (or if there's no specific reason, don't add that PRs)