RFR: 8293064: Remove unused NET_xxx functions

[Alan Bateman]

On Mon, 19 Sep 2022 18:34:22 GMT, Aleksei Efimov <aefimov at openjdk.org> wrote:

>> No tests were affected so this is purely a removal PR apart from updating copyright headers.
>> I ran tests for Tier 1,2&3 and everything seems to be passing
>
> The changes looks good to me with few additional changes needed on Linux platform: 
> - `NET_SetTrafficClass` can be also removed: It was discovered by invoking linker with `--print-gc-sections` option on a Linux-x64 platform. Header file: `net_util_md.h` Source file: `net_util_md.c`, both located in `src/java.base/unix/native/libnet`.
> - `NET_ThrowCurrent` on Linux (as already spotted by Daniel). It needs to be removed from `src/java.base/[unix|windows]/native/libnet/net_util_md.c`

@AlekseiEfimov InetAddress.ping is not asynchronously closable so I assume there is no need for the remaining NET_* functions to do sys calls that are wrapped with startOp/endOp. Just mentioning it because a future PR could remove a lot more, including the *_close.c files.

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PR: https://git.openjdk.org/jdk/pull/10343