Alias value not accessible through config object

[anyaevostinar]

Describe the bug
When you create an alias, you can't access it through the alias name methods of the config object.

To Reproduce
Steps to reproduce the behavior:
Assuming you've set up a config object with MUTATION_RATE with an alias MUTATION_RATE_ALIAS (as in the current test setup), attempting to then access the alias value throws error, i.e. by adding this line to the test file:

REQUIRE(config.MUTATION_RATE_ALIAS() > 0.098);

Expected behavior
Alias method should return value associated with it.

Toolchain (please complete the following information):

• OS: Mac Ventura 13.4.1
• Empirical Version: main

H/T to @K-Johnson-Horrigan for finding issue