SimpleAliasRegistry: extend test cases + small fix around alias overriding

[vincentstradiot]

Hi, here is a Pull Request that:

1. extends the existing SimpleAliasRegistryTests to cover the allowAliasOverriding functionality.
2. updates the implementation to fix a corner case issue in the SimpleAliasRegistry (explanation below).

Old behaviour was:

• register alias A -> B: ✅ OK
• register alias A -> A: ✅ OK
  • ⚠️ But alias A -> B was gone, which is not the expected behaviour as alias A -> B was overridden.

To my opinion, this should only be allowed if allowAliasOverriding = true, in exactly the same way as the existing implementation would only allow registering alias [A -> C] if allowAliasOverriding = true.

New behaviour:

• register alias A -> B: OK ✅
• register alias A -> A:
  • ✅ OK if allowAliasOverriding = true
  • ❌ Otherwise throws exception

Behaviour covered the following test cases in this PR:

• SimpleAliasRegistryTests.registerAliasWithSameName_GivenAliasOverridingAllowed_ThenReplacesExistingAlias
• SimpleAliasRegistryTests.registerAliasWithSameName_GivenAliasOverridingNotAllowed_ThenThrowsException

Thank you for the review, and have a nice day.