Support caller_is_root - main code added

[olahfemi]

Summary

Closes #_

• y/n | Does it introduce breaking changes?
• y/n | Is it dependant on the specific version of cargo-contract or pallet-contracts?

Description

Checklist before requesting a review

• My code follows the style guidelines of this project
• I have added an entry to CHANGELOG.md
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

[cmichi]

Thanks for the PR, generally the right direction. The function should be implemented analog to caller_is_origin:

ink/crates/env/src/engine/on_chain/impls.rs

Lines 672 to 677 in a0b2dce

	fn caller_is_origin<E>(&mut self) -> bool
	where
	E: Environment,
	{
	ext::caller_is_origin()
	}

.

If you have full-text search the repository for caller_is_origin you'll find the other places where code needs to be added (on_chain/impls.rs).