Update certificates used in TLS tests to use RSA keys & SHA-256 signature algorithm so that TLSv1.3 support can be added

[lhotari]

Problem

In TLSv1.3, certificates using SHA-1 signature algorithm are considered legacy and it's not recommended that TLSv1.3 implementations accept certificates that use SHA-1 signature algorithms.

In RFC8446, section 4.4.2.4. Receiving a Certificate Message
SHA-1 is deprecated, and it is RECOMMENDED that any endpoint receiving any certificate which it would need to validate using any signature algorithm using a SHA-1 hash abort the handshake with a "bad_certificate" alert.

Support for Digital Signature Algorithm (DSA) is also removed in TLSv1.3:

In RFC8446, section 1.2 Major Differences from TLS 1.2
Other cryptographic improvements were made, including changing the RSA padding to use the RSA Probabilistic Signature Scheme (RSASSA-PSS), and the removal of compression, the Digital Signature Algorithm (DSA), and custom Ephemeral Diffie-Hellman (DHE) groups.

Solution

Update all certificates (server and client) used in Pulsar tests to use RSA keys & SHA-256 signature algorithms so that it's possible to add TLSv1.3 support.

Additional context

#8580, #8581

TLSv1.3 is available in Java 8 since 8u161 (since OpenJDK 8u272).

[tisonkun]

@lhotari what's the status of this issue today?