After (as part of #15147) making ASN1_{,item_}d2i_bio() conservative on the error queue
by replacing ERR_clear_error() by ERR_set_mark() and friends, I got very weird regressions on private key file loading etc.

It took me a hell lot of work to find out that this is due to a nasty design of asn1_d2i_read_bio() and its sub-functions: unless the error queue is emptied initially, they go wrong causing all sorts of test failures related to OSSL_STORE.

The design should be changed to avoid such brittle behavior.

If not possible in the near future,

• this unexpected behavior should be clearly documented at the code line containing ERR_clear_error()
• documentation of functions calling asn1_d2i_read_bio() should mention that unfortunately they clear the error queue.