Adds support for 'caller_is_root'

[olahfemi]

Summary

Closes #_

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

This PR aims to add support for the caller_is_root function as requested by this issue

Description

Since the caller_is_root function is similar to caller_is_origin, I looked for places where the latter was implemented and did the same for the former.

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

[olahfemi]

@cmichi Re: your comment:
I couldn't find SHA id of the commit that made many of the unrelated changes in my local log, so I created a new PR.

[cmichi]

@olahfemi There are some CI errors due to an unclosed delimiter. You can check this guide on how to run what the CI does locally.

[olahfemi]

@olahfemi There are some CI errors due to an unclosed delimiter. You can check this guide on how to run what the CI does locally.

@cmichi, the unclosed delimiter has been fixed, and many of the local verification steps are passing now.

The failed steps weren't as a result of my changes. What do you want us to do about that?

Also, if my latest commit seems to have changed many unrelated files, it's because of the master merge and local verification.

[cmichi]

It's likely that you are using a different nightlyv version locally to execute the cargo +nightly fmt --all. Could you try

rustup update nightly
cargo +nightly fmt --all

And push the changes?

[cmichi]

Alternatively: can you allow me to edit your PR as described here?

[olahfemi]

I've updated the nightly version, reran fmt and pushed the changes. Also, maintainers have edit access to the PR, so you can make edits if necessary.