Create escape hatch for un-enumerated operating systems in `@{Enabled,Disabled}OnOs`

[mpkorstanje]

Currently the @EnabledOnOs and @DisabledOnOs annotations work with an enum to indicate the operating system. While the number of times we've added an OS is small, this is not an enumerable set. And it would benefit users if they can disable tests on a specific OS without having to wait for a new release.

• Support IBM AIX in @EnabledOnOs and @DisabledOnOs #1412
• @DisabledOnOs does not work on Solaris #1603
• Support NetBSD and DragonFlyBSD in @EnabledOnOs and @DisabledOnOs #5709

As such it would make sense to make it possible to use the annotation with an arbitrary operating system. I.e:

@DisabledOnOs(name = "AmongOS")
void test(){

}

Open question: How should the name be matched against System.getProperty("os.name")? With .toLowerCase().equals or .toLowerCase().contains?

Deliverables

• Escape hatch in @EnabledOnOs and @DisabledOnOs

[sbrannen]

Open question: How should the name be matched against System.getProperty("os.name")? With .toLowerCase().equals or .toLowerCase().contains?

For consistency, I'd go with what we already do in determineCurrentOs():

String name = annotation.name();
String osName = System.getProperty("os.name");
// ...
if (osName.toLowerCase(Locale.ENGLISH).contains(name)) {
    // ...
}

[dbwiddis]

Since it was my PR that prompted this, I'm currently working around it with:

@EnabledIfSystemProperty(named = "os.name", matches = "(?i)netbsd")

It's not a hard blocker, but I like consistency.