Use JUnit 5 instead of JUnit 4

[asomov]

• the test are not changed
• commented out tests were not migrated

[codecov[bot]]

Codecov Report

Merging #55 into master will not change coverage by %. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #55   +/-   ##
=========================================
  Coverage     30.67%   30.67%           
  Complexity      185      185           
=========================================
  Files            57       57           
  Lines          1816     1816           
  Branches        273      273           
=========================================
  Hits            557      557           
  Misses         1186     1186           
  Partials         73       73           

Impacted Files	Coverage Δ	Complexity Δ
...tor/src/main/kotlin/actor/proto/DeferredProcess.kt	87.50% <ø> (ø)	4.00 <0.00> (ø)
...roto-actor/src/main/kotlin/actor/proto/java/API.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)
...or/src/main/kotlin/actor/proto/java/ContextImpl.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)
...in/kotlin/actor/proto/mailbox/DefaultDispatcher.kt	100.00% <ø> (ø)	2.00 <0.00> (ø)
...ain/kotlin/actor/proto/mailbox/MailboxProducers.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)
...ain/kotlin/actor/proto/router/GroupRouterConfig.kt	100.00% <ø> (ø)	2.00 <0.00> (ø)
...main/kotlin/actor/proto/router/PoolRouterConfig.kt	100.00% <ø> (ø)	2.00 <0.00> (ø)
...outer/src/main/kotlin/actor/proto/router/Router.kt	50.00% <ø> (ø)	5.00 <0.00> (ø)
.../src/main/kotlin/actor/proto/router/RouterActor.kt	76.19% <ø> (ø)	6.00 <0.00> (ø)
...src/main/kotlin/actor/proto/router/RouterConfig.kt	100.00% <ø> (ø)	2.00 <0.00> (ø)

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[guenhter]

Well done!