[SPARK-45378][CORE] Add convertToNettyForSsl to ManagedBuffer

[hasnain-db]

What changes were proposed in this pull request?

As the title suggests. In addition to that API, add a config to the TransportConf to configure the default block size if desired.

Why are the changes needed?

Netty's SSL support does not support zero-copy transfers. In order to support SSL using Netty we need to add another API to the ManagedBuffer which lets buffers return a different data type.

Does this PR introduce any user-facing change?

No

How was this patch tested?

CI. This will have tests added later - it's tested as part of #42685 from which this is split out.

Was this patch authored or co-authored using generative AI tooling?

No

[hasnain-db]

cc: @mridulm@JoshRosen this is now ready to review and has all green tests on CI

[mridulm]

QQ: If/when there is more widespread adoption of kernel.ssl.sendfile (and ssl_sendfile from openssl), how will it impact the proposed design ?

[hasnain-db]

@mridulm once it's widely adopted and supported in Netty + netty-tcnative, we can remove these APIs and potentially just use convertToNetty, depending on how the design is from the netty side. But it's unclear to me what the timelines are for that

[mridulm]

Sounds good, can you add a comment to that effect in the Trait ?
Rest looks good to me

[mridulm]

Pending CI
+CC @JoshRosen

[hasnain-db]

CI is also finally green here

[mridulm]

Merged to master.
Thanks for working on this @hasnain-db !
Thanks for review @JoshRosen :-)