HDDS-9992. Add static import for assertions and mocks in ozone-s3gateway

[wzhallright]

What changes were proposed in this pull request?

The goal of this task is to add import static for all assertions and interactions with mocks. Replacing:

Assertions.assert<X>(...) -> assert<X>(...)
Assertions.fail(...) -> fail(...)

and

Mockito.mock(...) -> mock(...)
Mockito.verify(...) -> verify(...)
Mockito.when(...) -> when(...)

and

ArgumentMatchers.any() -> any()
ArgumentMatchers.eq() -> eq()
ArgumentMatchers.matches() -> matches()
// also:
// Matchers.<...>()

makes the code more readable (shorter lines, less wrapping).

What is the link to the Apache JIRA

HDDS-9992

CI

https://github.com/wzhallright/ozone/actions/runs/7318668302

[adoroszlai]

Thanks @wzhallright for the patch.