Decouple SuiteRunner and TestRunner

[krmahadevan]

Closes #2928

Fixes #2928 .

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[missedone]

@krmahadevan , it could be a breaking change for testng-remote https://github.com/testng-team/testng-remote/blob/master/remote7_8/src/main/java/org/testng/remote/support/RemoteTestNG7_8.java#L33-L36
where can I take a testng snapshot jar to test out?

[krmahadevan]

@missedone - I dont think there is going to be any impact because of this change, because SuiteRunner implements the newly added interface.

But you can find the snapshot here to test it out https://oss.sonatype.org/content/repositories/snapshots/org/testng/testng/7.9.0-SNAPSHOT/

[missedone]

just verified that it breaks testng-remote
no worries, i will create the adapter for testing 7.9.0

[RemoteTestNG] detected TestNG version 7.9.0
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
java.lang.NoSuchMethodError: 'void org.testng.TestRunner.<init>(org.testng.internal.IConfiguration, org.testng.ISuite, org.testng.xml.XmlTest, boolean, java.util.Collection, java.util.List, org.testng.SuiteRunner)'
	at org.testng.remote.support.RemoteTestNG7_8$1.newTestRunner(RemoteTestNG7_8.java:34)
	at org.testng.remote.support.RemoteTestNG7_8$DelegatingTestRunnerFactory.newTestRunner(RemoteTestNG7_8.java:67)
	at org.testng.ITestRunnerFactory.newTestRunner(ITestRunnerFactory.java:52)
	at org.testng.SuiteRunner$ProxyTestRunnerFactory.newTestRunner(SuiteRunner.java:720)
	at org.testng.SuiteRunner.init(SuiteRunner.java:224)
	at org.testng.SuiteRunner.<init>(SuiteRunner.java:116)
	at org.testng.TestNG.createSuiteRunner(TestNG.java:1373)
	at org.testng.TestNG.createSuiteRunners(TestNG.java:1347)
	at org.testng.TestNG.runSuitesLocally(TestNG.java:1189)
	at org.testng.TestNG.runSuites(TestNG.java:1112)
	at org.testng.TestNG.run(TestNG.java:1080)
	at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:115)
	at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:251)
	at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:77)