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.
• If contributing template-only or documentation-only changes which will change sample output, build the project before.
• Run the shell script(s) under ./bin/ (or Windows batch scripts under.\bin\windows) to update Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit, and these must match the expectations made by your contribution. You only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the code or mustache templates for a language ({LANG}) (e.g. php, ruby, python, etc).
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