feat: root call mod with new CallError

[lwshang]

Description

The Call struct API was added to the existing src/api/call.rs module.
This PR moves the new API to src/call.rs module.
The src/api/call.rs is consistent with the main branch with some minor adjustment for the new ic0 crate.

The src/call.rs module also got some refreshment.

pub type CallResult<R> = Result<R, CallError>;

pub enum CallError {
    #[error("Failed to encode the arguments: {0}")]
    CandidEncodeFailed(String),

    #[error("The IC was not able to enqueue the call with code {0:?}")]
    CallPerformFailed(CallPerformErrorCode),

    #[error("The call was rejected with code {0:?} and message: {1}")]
    CallRejected(RejectCode, String),

    #[error("Failed to decode the response as {0}")]
    CandidDecodeFailed(String),
}

How Has This Been Tested?

e2e tests

Checklist:

• The title of this PR complies with Conventional Commits.
• I have edited the CHANGELOG accordingly.
• I have made corresponding changes to the documentation.