[PHP] fix php codegen ordering issue with CodegenSecurity

[sebastien-rosset]

Fix transient build issues with PHP symfony. The generated list of authMethods in codegen is not sorted because it is in a HashSet, hence the output is not deterministic. This means the generated code may potentially change when the code is executed or when the hash code changes.

I think codegen should return collections in a deterministic order, such that when generating samples (in the bin directory), it does not keep swapping generated code around.

PR checklist

• Read the contribution guidelines.
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[macjohnny]

@sebastien-rosset thanks for the PR!

[sebastien-rosset]

Thanks for merging quickly!