Add byte-number conversion utilities to xod/bits

[nkrkv]

Rationale

Bytes are only used to store and transfer data. On the other hand, numbers are more applicative. We need a sane way to convert between numbers and bytes. Let’s add a few nodes to xod/bits:

• i8-to-number
• u8-to-number
• i16-to-number
• u16-to-number (same as xod/core/word-to-number)
• i32-to-number
• u32-to-number
• number-to-i8
• number-to-u8
• number-to-i16
• number-to-u16
• number-to-i32
• number-to-u32

Here, i means signed and u is unsigned. The number denotes number of bits from the byte-data side. For example, number-to-i32 have a single number input and four byte outputs. The number is considered to be integer: a fractional part is truncated if present in the input.

To serialize numbers as is, let’s implement a couple of additional nodes:

• ieee754-to-number — takes four bytes and returns a single number
• number-to-ieee754

Prerequisites

#1185, #1187

Acceptance criteria

• The nodes listed are implemented in xod/bits
• The xod/core/word-to-number is deprecated
• All new nodes are documented
• All new nodes have table tests