Add test coverage for PKCS7_TEXT mode

Add test coverage for PKCS7_TEXT mode

This was inspired by the following commit
9882d389df71 ("crypto/pkcs7/pk7_smime.c: Add BIO_free() to avoid memory leak")
which discovered a bug in PKCS7_verify(..., PKCS7_TEXT).
While there is some test coverage for PKCS_verify by
./test/pkcs7_test.c, there is no test coverage whatsoever
of the PKCS7_TEXT flag for PKCS7_sign, PKCS7_encrypt and
PKCS7_decrypt.
So this adds some test coverage for those functions as well.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28223)

(cherry picked from commit d582adc672bca4bc71a7766bb692558086efdd69)