Use different certificate types in Networking tests with dynamically generated certificates.

[rzikm]

Suggested by bartonjs in #116098 (comment)

When no keyFactory is provided, BuildPrivatePki hashes all the inputs to create a stable offset against whatever algorithms are available

Assuming the problem is just that RSA-1024 was too small, we could change the size used in CertificateAuthority to use a preprocessor directive to know if it's the crypto tests (where we want smaller so it's faster) or networking (where you need a larger smallest size).

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