feat: improve events contract to be usable via dynamic link

[loloicci]

Description

This PR improves the events contract to be useable as a dynamic linked contract. This contract is used by tests implemented in wasmvm's PR.
This was a part of #269.

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.