[test] remove PowerMockito from the classpath and replace the usages with Mockito

[nicoloboschi]

Motivation

PowerMockito (mockito extension built on PowerMock) can be totally replaced with Mockito.
In this way we can remove the dependency powermock-api-mockito2.

We can also remove powermock-module-testng artifact (and in turn powermock-core) since it's not used anymore.
The only artifact that doesn't have a simple replace path is powermock-reflect which will remain in the classpath.

The main reason behind the PowerMock usage reduction is that the project is semi-abandoned and it can easily break with newer jdk versions.

Modifications

• Replaced PowerMockito with Mockito classes (just changing the packages)
• Replaced PowerMockito constructor mock with Mockito MockedConstruction feature.
• Removed the module powermock-module-testng in favor of powermock-reflect

Documentation

• no-need-doc

[eolivelli]

Lgtm as far as CI passes.

Please note that this patch will make it harder to cherry pick patches.

Please take into consideration a port to at least branch 2.9 and 2.8

[eolivelli]

Putting state into 'requested change' until CI passes

[nicoloboschi]

/pulsarbot rerun-failure-checks

[nicoloboschi]

@eolivelli CI is green

[nicoloboschi]

@lhotari @shoothzj @michaeljmarshall @codelipenghui PTAL

[lhotari]

Awesome!