Zero copy file transferring (via FileRegion) is disabled for IoUring transport.

[doxlik]

Hello dear Vert.x team.

As I see, in the IoUringTransport the support of file region is disabled by

public class IoUringTransport implements Transport {
...
  @Override
  public boolean supportFileRegion() {
    return false;
  }
...

which mean that Http1xServerResponse.sendFile function will always fallback to read / write model instead of zero copy.

And as Netty have direct support for file regions over io_uring (via IoUringFileRegion) I think it is good idea to enable this support for Vert.x as well, what do you think?

P.S. I tried to "hack" transport just to make this getter return true (via Unsafe) and IoUringFileRegion start to work BUT it has constant fd leak, actually they were never closed and I thought that probably it is bug of IoUringFileRegion but I check in reactor-netty lib and it utilizing IoUringFileRegion don't have leak which mean my hack was not enough and we also need somewhere handle FileRegion closure / releasing and as you have super huge experience with Netty and DefaultFileRegion I think handling IoUringFileRegion will not cause big problems for you.

Thank you for bringing such perfect software as Vert.x to JVM community)