Improve file reading

[vinc]

• Rename api::fs::read(path) to api::fs::read_to_bytes(path)
• Add api::fs::read(path, buf)
• Move api::fs::canonicalize(path) to kernel internal in sys::fs
• Add (read-bytes <path> <len>) to read len bytes from a file in lisp
• Add (bytes <str>) to transform a string into a list of bytes in lisp
• Add (str <bytes>) to transform a list of bytes into a string in lisp
• Add progn (aliased to do) to evaluate a sequence of expression in lisp

[vinc]

> (read-bytes "/tmp/alice.txt" 5)
(65 76 73 67 69)

> (str (read-bytes "/tmp/alice.txt" 5))
"ALICE"

> (first (read-bytes "/dev/random" 1))
145

> (first (read-bytes "/dev/random" 1))
114

> (first (read-bytes "/dev/random" 1))
10

[vinc]

This example read the console to detect the ANSI escape code ^[A for cursor up:

> (defn read-char () (read-bytes "/dev/console" 4))
read-char

> (eq (do (read-char) (read-char) (read-char)) (bytes "A"))
true