Improve crypto hashing APIs to add salt

[ldclakmal]

Description:
The current hashing APIs of ballerina/crypto library does not support to add "salt".
Ex. crypto:hashSha256(password)

It would better to improve the existing APIs for the above use case.
Suggested API: public isolated function hashSha256(byte[] input, byte[] salt) returns byte[]

Java Implementation:

SecureRandom random = new SecureRandom();
byte[] salt = new byte[16];
random.nextBytes(salt);

byte[] password = "alice@123".getBytes();

MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(salt);
byte[] hashedPassword = md.digest(password);

With this approach, there can be another requirement for the use cases of secure random generators. Refer to the "Secure Random Number" section under "Crypto" tab of "[Research] Comparison on Ballerina Security Features / APIs" [1].

Also, there should be a hash verification API as well.

[1] https://docs.google.com/spreadsheets/d/1PyMAlAvgkEL0RpW8CVUj1ccW_61Vm6SMbvadFVYRpSA/edit?usp=sharing