Derive orderlessness for special elements and repetition operators

The following should be orderless in standard contexts:

- Multiplication of terms/exponentials with the same base. (`x*x`, `x^3 * x`, `x^3 * x^2`, etc.)
- Application of identity. (`x + zero(x)`, `x * one(x)`, etc.)
- Application of annhilator. (`x * zero(x)`, `x & false`, `x | true`, etc.)

The issue names no files, tests, or entry points. First locate the existing orderlessness and rewrite handling in Simplify.jl, then verify the listed multiplication, identity, and annihilator examples in standard contexts. Done means those cases simplify without depending on operand order.

Written by the indexing model from the issue text.