Adding extensions is fragile, with the TLSEXT_TYPE entry needing to be
located at TLSEXT_IDX in the array.
This adds a test to ensure extensions are in the correct order.
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19269)
