Inconsist query builder method names

[ghost]

• Laravel Version: 8.0.0
• PHP Version: 7.4.0
• Database Driver & Version: doesn't matter

Description:

There is a selectRaw method for query builder, I think this should be renamed to addSelectRaw, so it will be consistent with addSelect(DB::raw(...)) as documentation says.

selectRaw feels more like the raw version of the select method itself.

I suggest we deprecate selectRaw and add a new addSelectRaw method.