DynamicPortsBundle should allow custom port finder

[sleberknight]

With the addition of #536 , PortAssigner can accept a FreePortFinder to determine how to find free ports.

This task is to modify DynamicPortsBundle to permit assignment of a FreePortFinder, which will need to be added to DynamicPortsConfiguration.

[sleberknight]

After looking into this more, I found that the PortAssigner really doesn't need a LocalPortChecker anymore, since the FreePortFinder is now responsible for finding ports. After release 3.9.0 when the FreePortFinder was added, the only time the LocalPortChecker is used is if the FreePortFinder is not specified when building a PortAssigner. In that case, the behavior in the constructor is to create a new RandomFreePortFinder instance and pass the LocalPortChecker to its constructor. Here is the relevant part of the constructor implementation:

@Builder
private PortAssigner(LocalPortChecker localPortChecker,
                     TlsContextConfiguration tlsConfiguration,
                     PortAssignment portAssignment,
                     FreePortFinder freePortFinder,
                     @Nullable AllowablePortRange allowablePortRange,
                     ServerFactory serverFactory,
                     PortSecurity portSecurity) {

    this.localPortChecker = Optional.ofNullable(localPortChecker).orElse(new LocalPortChecker());

    // ...other assignments elided...

    this.freePortFinder = Optional.ofNullable(freePortFinder)
            .orElseGet(() -> new RandomFreePortFinder(this.localPortChecker));

     // ...more assignments elided...
}

But if a FreePortFinder is supplied to the PortAssigner builder, then the localPortChecker field is never used. This was an oversight when I added FreePortFinder, since the previous behavior was to use the localPortChecker when finding ports. Once that behavior was removed from PortAssigner, the localPortChecker field really serves no purpose anymore. As a result, we should remove it from PortAssigner. Note this will be a breaking API change and thus cause a major version bump to 4.0.0.