Use common formatting for backtraces (#6977)

This makes debug_print_backtrace() use the same formatting as exception
backtraces. The only difference is that the final #{main} is omitted,

Use common formatting for backtraces (#6977)

This makes debug_print_backtrace() use the same formatting as exception
backtraces. The only difference is that the final #{main} is omitted,
because it wouldn't make sense for limited backtraces, and wasn't there
previously either.

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Set opcache.optimization_level=0 in test

Otherwise opcache "inlines" the function, which causes a minor
difference in destruction behavior.

Test fixes

Fixed bug #78973

Save opline in leave helper to correctly handle destructor calls
during CV freeing (or other leave freeing).