Update crypto HMAC APIs and refactor code

[ldclakmal]

Purpose

This PR updates the ballerina/crypto module API for HMAC operations with the return of crypto:Error.

Old APIs:

public isolated function hmacMd5(byte[] input, byte[] key) returns byte[];
public isolated function hmacSha1(byte[] input, byte[] key) returns byte[];
public isolated function hmacSha256(byte[] input, byte[] key) returns byte[];
public isolated function hmacSha384(byte[] input, byte[] key) returns byte[];
public isolated function hmacSha512(byte[] input, byte[] key) returns byte[];

Updated APIs:

public isolated function hmacMd5(byte[] input, byte[] key) returns byte[]|Error;
public isolated function hmacSha1(byte[] input, byte[] key) returns byte[]|Error;
public isolated function hmacSha256(byte[] input, byte[] key) returns byte[]|Error;
public isolated function hmacSha384(byte[] input, byte[] key) returns byte[]|Error;
public isolated function hmacSha512(byte[] input, byte[] key) returns byte[]|Error;

Fixes: ballerina-platform/ballerina-library#908
Related to: ballerina-platform/ballerina-library#584