[test] Vertically test explicit EC params API patterns

This commit adds a new test (run on all the built-in curves) to create
`EC_GROUP` with **unknown** *explicit parameters*: from a built-in group
we create an alternative group from scratch that differs in the
generator used.

At the `EC_GROUP` layer we perform a basic math check to ensure that the
math on the alternative group still makes sense, using comparable
results from the origin group.

We then create two `EC_KEY` objects on top of this alternative group and
run key generation from the `EC_KEY` layer.

Then we promote these two `EC_KEY`s to `EVP_PKEY` objects and try to
run the derive operation at the highest abstraction layer, comparing
results in both directions.

Finally, we create provider-native keys using `EVP_PKEY_fromdata` and
data derived from the previous objects, we compute an equivalent shared
secret from these provider keys, and compare it to the result obtained
from the previous steps.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/12507)

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