RFR: 8244202: Implementation of JEP 418: Internet-Address Resolution SPI [v4]

[Aleksei Efimov]

> This change implements a new service provider interface for host name and address resolution, so that java.net.InetAddress API can make use of resolvers other than the platform's built-in resolver.
> 
> The following API classes are added to `java.net.spi` package to facilitate this:
> - `InetAddressResolverProvider` -  abstract class defining a service, and is, essentially, a factory for `InetAddressResolver` resolvers.
> - `InetAddressResolverProvider.Configuration ` - an interface describing the platform's built-in configuration for resolution operations that could be used to bootstrap a resolver construction, or to implement partial delegation of lookup operations.
> - `InetAddressResolver` - an interface that defines methods for the fundamental forward and reverse lookup operations.
> - `InetAddressResolver.LookupPolicy` - a class whose instances describe the characteristics of one forward lookup operation.  
> 
> More details in [JEP-418](https://openjdk.java.net/jeps/418).
> 
> Testing: new and existing `tier1:tier3` tests

Aleksei Efimov has updated the pull request incrementally with four additional commits since the last revision:

 - Remove no longer used import from IPSupport
 - Rename IPSupport.hasAddress and update it to use SocketChannel.open
 - Address review comments: javadoc + code cleanup
 - Address resolver bootstraping issue

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5822/files
  - new: https://git.openjdk.java.net/jdk/pull/5822/files/d302a49a..ac0d2184

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5822&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5822&range=02-03

  Stats: 245 lines in 5 files changed: 180 ins; 35 del; 30 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5822.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5822/head:pull/5822

PR: https://git.openjdk.java.net/jdk/pull/5822