compiletest: consider rejecting conditional test execution directives being used together with unconditional test disabling directives

[jieyouxu]

Remark: useless/misleading //@ run-pass in a few aux files that are //@ ignore-test (//@ ignore-auxiliary)

Originally posted by @jieyouxu in #139967 (comment)

Consider rejecting combination of

• Conditional test execution directives (e.g. //@ ignore-*), with
• Unconditional test execution directives (e.g. //@ ignore-test),

Since the unconditional test ignore will "absorb" conditional ones. Probably do this after reworking directive handling.