Implement an ossltest provider to replace ossltest engine

Implement an ossltest provider to replace ossltest engine

Part of the effort to remove engines creates a problem for our test
suite, in that we have a large number of tests that rely on the use of a
test engine (ossltest), which implements the aes-128-cbc, aes-128-gcm,
aes-128-cbc-hmac-sha1 ciphers, several digests and a random number
generator to produce predictable outputs for the purposes of doing
testing against known values.

Since we're getting rid of engines, these tests need to be updated to
use a provider that presents the same functionality.

This commit implements that provider.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/28461)