Add input validation

[dastanbeksamatov]

Input validation

• Currently most of our Runtime APIs do not validate the incoming input and throws generic Runtime: Unreachable error. In most of the cases, when we receive the input, we decode it to the desired type and expect it to be encoded correctly. For instance, in /api/others.ts in function system_accountNonce we decode input to AccountId like this

const account = AccountId.fromU8Array(input).result.

which does not assume the case when input might be encoded incorrectly.

TO-DO

• Implement new function/tool that validates each input incoming to the runtime and returns corresponding error code and message.