operationId: Allow getting only the method name

[ygalblum]

This PR adds the functionality I requested in #9719

Add new configuration flags: REMOVE_OPERATION_ID_PREFIX_DELIMITER and REMOVE_OPERATION_ID_PREFIX_COUNT
Add the corresponding fields in the DefaultCodegen
Sanitize the operationId according to the new fields
Add delimiter to list of nonNameElementPattern
Add unit test for different cases (different delimiters and counts)

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fixes #9719

[wing328]

cc @OpenAPITools/generator-core-team

[wing328]

@ygalblum thanks for the PR, which looks good to me 👍