feat: improve how to specify the callee contract address

[loloicci]

Description

This PR changes how to specify the callee contract address in the caller contract.
For this purpose, it contains

• Define the Contract trait that represents the callee contract
• Implement a derive macro for Contract
• Modify the VM code to change from where the contract address is fetched
• Modify the dynamic_link macro

What is changed about the usage of the #[dynamic_link] macro is described in #207.

Closes #207

Types of changes

• Bug fix (changes which fixes an issue)
• New feature (changes which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• ETC (build, ci, docs, perf, refactor, style, test)

Checklist

• I followed the contributing guidelines.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• The PR title and commits are followed conventional commit form.

[tnasu]

Almost LGTM. Would you fix the checks error?
https://github.com/line/cosmwasm/runs/7124425608?check_suite_focus=true

[loloicci]

@tnasu

Would you fix the checks error?
https://github.com/line/cosmwasm/runs/7124425608?check_suite_focus=true

I checked them with integration tests and missed fixing some unit tests. Now I fixed and pushed.
Thank you for your check!

[shiki-tak]

LGTM