RFR: 8274883: (se) Selector.open throws IAE when the default file system provider is changed to a custom provider [v2]

[Maxim Kartashev]

> The gist of the problem: when a file system is specified via `-Djava.nio.file.spi.DefaultFileSystemProvider`, a call to `SelectorProvider.provider().openSelector()` ends with a throw on Windows.
> 
> There are two distinct components to the problem:
> 
> 1. `ExceptionInInitializerError` is thrown during the static initialization of the `UnixDomainSockets.UNNAMED` field even though it isn't used on this code path (see `UnixDomainSocketAddress.of()` that throws `IllegalArgumentException` if invoked on a path from a non-default file system). 
> This is fixed by lazy-initializing the static member `UNNAMED` of `UnixDomainSockets` so that this initialization doesn't throw unless actually used.
> 
> 2. `IllegalArgumentException` is thrown by `UnixDomainSocketAddress.of()`  later on when `ServerSocketChannel` tries to use Windows version of `PipeImpl` and its method `createListener()` specifically. That `PipeImpl` probes for the availability of Unix Domain Sockets by trying to bind to a unique temporary name. That call throws `IAE` when a non-default Java file system is installed while the probing code (`PipeImpl.createListener()`) only expects `UnsupportedOperationException` or `IOException`.
> The fix is to re-throw `UOE` instead of `IAE` in `UnixDomainSockets.genrateTempName()`. This is more consistent with the definition of the exception purpose ("requested operation is not supported"). So with this change, a loopback network socket will be used to implement a pipe on a non-default Java file system. Also, pipes do not rely on the default Java file system on other platforms (Linux, MacOS) as well.
> 
> Tested by running `jtreg:test/jdk/java/nio` on Window, MacOS, and Linux.

Maxim Kartashev has updated the pull request incrementally with one additional commit since the last revision:

  Addressed PR comments:
  
  - renamed UNNAMEDHolder to UnnamedHolder,
  - renamed getUNNAMED() to unnamed(),
  - replaced catch IllegalArgumentException with a check for the provider.

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6722/files
  - new: https://git.openjdk.java.net/jdk/pull/6722/files/1b7d0b9f..8dcc88e3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6722&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6722&range=00-01

  Stats: 19 lines in 2 files changed: 8 ins; 6 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6722.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6722/head:pull/6722

PR: https://git.openjdk.java.net/jdk/pull/6722