feat(Rust API): Implement Rust Cron Module

[saibatizoku]

Description

Adds implementation of Rust Cron Module.

Related Issue(s)

List the issue numbers related to this pull request.

Closes #93

Description of Changes

• Adds a state to store and manage crontabs
• Implements all of the cron API methods with documentation.

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[Mr-Leshiy]

Does it make sense to move all internal cron logic as like mkdelay_crontab, mkcron_impl etc. out of the host.rs ? Like it is already done for hash runtime extensions https://github.com/input-output-hk/hermes/blob/main/hermes/bin/src/runtime_extensions/hermes/hash/host.rs.

Also I think it is needed to add some unit tests for such functions as mkcron_impl, cron_time_to_cron_sched etc.

[saibatizoku]

Does it make sense to move all internal cron logic as like mkdelay_crontab, mkcron_impl etc. out of the host.rs ? Like it is already done for hash runtime extensions https://github.com/input-output-hk/hermes/blob/main/hermes/bin/src/runtime_extensions/hermes/hash/host.rs.

Also I think it is needed to add some unit tests for such functions as mkcron_impl, cron_time_to_cron_sched etc.

It should be ready to go.

[Mr-Leshiy]

LGTM