feat: call trace tree & etherscan caching

[DanielSchiavini]

Important for reviewers

• This PR contains https://github.com/vyperlang/titanoboa/pull/239 - that one may be merged separately or together via this PR (diff between the two PRs).
• Fixes #81

What I did

Allow users to generate a call tree of the last message call

How I did it

• Add call_trace method to the base EVM contract
• Allow trace to be printed or exported to HTML
• Add optional caching for ethercan when requests_cache is installed
• Fixed a bug in the ABI parser
• Test the interaction between ABI and Vyper contracts

How to verify it

• Tests are included

Description for the changelog

• Allow users to generate a call tree of the last message call

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