Fix processing for prompt select_account with consent

Multiple prompt values are allowed and this change fixes the check for
select_account if it was used together with other prompt values. Where
select_account previously was ignored, it is now processed as required,
fixing the use case when a RP wants to trigger select_account first
while at the same time wants also to request interactive consent.
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Gitea Version: 1.28.0+dev-477-g8b6ad49a5f