rename integer literal type and float literal type

[andrewrk]

Right now,

• @typeName(@typeOf(1)) is "(integer literal)"
• @typeName(@typeOf(1.0)) is "(float literal)"

I propose that these are renamed to comptime_int and comptime_float respectively. You would be able to refer to the types directly by name.

Also rename

• @import("builtin").TypeId.FloatLiteral to ComptimeFloat
• @import("builtin").TypeId.IntLiteral to ComptimeInt
• @import("builtin").TypeId.UndefinedLiteral to Undefined
• @import("builtin").TypeId.NullLiteral to Null