Apollo codegen doesn't return non-zero exit code when errors have been found

**Intended outcome:**
Running `apollo client:codegen ...` should exit with a number different than 0, when there are errors.

**Actual outcome:**
Running `apollo client:codegen ...` exits by returning 0, even when there are errors. Such as **Error: ️️There are multiple definitions for the AccountSelectorInputQuery operation. All operations in a project must have unique names. If generating types, only the types for the first definition found will be generated.**. This turns out to be problematic on a pipeline where the next command shouldn't be executed, if there are errors on the previous one.

**How to reproduce the issue:**
Create two queries with the same name and run the `apollo client:codegen ...` command. Then run `echo $?` to get its return value. It is 0 but should be different, since there was an error.

**Versions**
2.21.3

Start by reproducing the issue with two queries sharing the same operation name, then run `apollo client:codegen ...` and inspect the `echo $?` result. Trace the `apollo client:codegen` command's error handling and verify that duplicate-definition errors produce a non-zero exit code so subsequent pipeline commands can stop.

Written by the indexing model from the issue text.