Refactor code to use modern Buffer creation API

[jozefizso]

1. Refactor code to use modern Buffer.alloc() with zero-filled memory
2. Refactor code to use modern Buffer.from() creation api

Fixes the 'new Buffer()' was deprecated since v6.0.0. Use 'Buffer.alloc()' or 'Buffer.from()' instead. (n/no-deprecated-api) error reported by npx standard linter.

Buffer Creation API

In versions of Node.js prior to 6.0.0, Buffer instances were created using the Buffer constructor function, which allocates the returned Buffer differently based on what arguments are provided:

• Passing a number as the first argument to Buffer() (e.g. new Buffer(10)) allocates a new Buffer object of the specified size. Prior to Node.js 8.0.0, the memory allocated for such Buffer instances is not initialized and can contain sensitive data. Such Buffer instances must be subsequently initialized by using either buf.fill(0) or by writing to the entire Buffer before reading data from the Buffer. While this behavior is intentional to improve performance, development experience has demonstrated that a more explicit distinction is required between creating a fast-but-uninitialized Buffer versus creating a slower-but-safer Buffer. Since Node.js 8.0.0, Buffer(num) and new Buffer(num) return a Buffer with initialized memory.

• Passing a string, array, or Buffer as the first argument copies the passed object's data into the Buffer.

• Passing an ArrayBuffer or a SharedArrayBuffer returns a Buffer that shares allocated memory with the given array buffer.

Reference: https://nodejs.org/docs/latest/api/buffer.html#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe