STORE: Fix OSSL_STORE_attach() to check |ui_method| before use
STORE: Fix OSSL_STORE_attach() to check |ui_method| before use

ossl_pw_set_ui_method() demands that the passed |ui_method| be
non-NULL, and OSSL_STORE_attach() didn't check it beforehand.

While we're at it, we remove the passphrase caching that's set at the
library level, and trust the implementations to deal with that on
their own as needed.

Fixes #12830

Reviewed-by: Tim Hudson <eb0be8e447f673b41b10eda09d63cd72526b0a42@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12831)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl