test: prepare for auto amending implicit use of "default" security policy

[toidiu]

Description of changes:

This PR includes the manual changes needed before running the auto-generate script in #4778

Changes include:

• adding s2n_auto_gen_old_default_security_policy which captures the current numbered equivalent of the default policies.
• changing comments from s2n_config_new() -> s2n_config_new so that the auto script can match on that string

Testing:

Only test files were changed and current tests should continue to pass.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[toidiu]

Implicit detection wont work so we need a better plan for that prior to making these manual changes.