Use a sound naming strategy when generating identifiers

### What is wrong?

We need to make sure names generated by the compiler can't collide with user-defined names or other names generated by the compiler.

### How can it be fixed

Add well-documented naming modules to the codegen libraries and use them when generating identifiers.

Start by locating the codegen libraries and every compiler path that generates identifiers; the issue does not name specific files or tests. Read the existing identifier-generation code and determine how generated names can be separated from user-defined and other generated names. Done means documented naming modules are used across those paths and collision cases are covered by tests.

Written by the indexing model from the issue text.