Forces to use sources compatible with java8 and runtime java 11

[skabashnyuk]

What does this PR do?

Forces to use sources compatible with java8 and runtime java 11.

In case of java 8 runtime

[INFO]
[INFO] --- maven-enforcer-plugin:3.0.0-M2:enforce (enforce-java-version) @ che-parent ---
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.RequireJavaVersion failed with message:
To build this project JDK 11 (or upper) is required. Please install it.
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for Che Parent 7.15.0-SNAPSHOT:

In case java 11 code

INFO] Changes detected - recompiling the module!
[INFO] Compiling 36 source files to /Users/skabashn/dev/src/redhat/che/core/commons/che-core-commons-lang/target/classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /Users/skabashn/dev/src/redhat/che/core/commons/che-core-commons-lang/src/main/java/org/eclipse/che/commons/lang/IoUtil.java:[73,34] cannot find symbol
  symbol:   method isBlank()
  location: variable name of type java.lang.String
[ERROR] /Users/skabashn/dev/src/redhat/che/core/commons/che-core-commons-lang/src/main/java/org/eclipse/che/commons/lang/IoUtil.java:[74,26] cannot find symbol
  symbol:   method repeat(int)
  location: class java.lang.String
[ERROR] /Users/skabashn/dev/src/redhat/che/core/commons/che-core-commons-lang/src/main/java/org/eclipse/che/commons/lang/IoUtil.java:[89,27] cannot find symbol
  symbol:   method isBlank()
  location: class java.lang.String
[ERROR] /Users/skabashn/dev/src/redhat/che/core/commons/che-core-commons-lang/src/main/java/org/eclipse/che/commons/lang/IoUtil.java:[89,46] cannot find symbol
  symbol:   method repeat(int)
  location: class java.lang.String
[INFO] 4 errors
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for Che Parent 7.15.0-SNAPSHOT:
[INFO]
[INFO] Che Parent ......................................... SUCCESS [  2.719 s]
[INFO] Che Core Parent .................................... SUCCESS [  0.091 s]
[INFO] Che Core :: Commons :: Parent ...................... SUCCESS [  0.078 s]
[INFO] Che Core :: Commons :: Annotations ................. SUCCESS [  3.074 s]
[INFO] Che Core :: Commons :: Java API extension classes .. FAILURE [  1.557 s]
[INFO] Che Core :: Commons :: Utilities for tests ......... SKIPPED

What issues does this PR fix or reference?

Since we might need to backport some feature for old branches it would be nice to keep source code in master java 8 compatible for some time

[che-bot]

✅ E2E Happy path tests succeed 🎉

See Details

• Jenkins job

• logs and configs

• Happy path tests DevFile

• image: maxura/che-server:17194

Tested with Eclipse Che Multiuser User on K8S (minikube v1.1.1)

[nickboldt]

works for me.

[skabashnyuk]

[ci-build]

[che-bot]

❌ E2E Happy path tests failed ❗

See Details

• Jenkins job

• test report

• logs and configs

• Happy path tests DevFile

• image: maxura/che-server:17194

Tested with Eclipse Che Multiuser User on K8S (minikube v1.1.1)

ℹ️ Use comment "[crw-ci-test]" to rerun happy path E2E test.

[skabashnyuk]

[crw-test]

[skabashnyuk]

[crw-ci-test]

[skabashnyuk]

ci-build

[che-bot]

✅ E2E Happy path tests succeed 🎉

See Details

• Jenkins job

• logs and configs

• Happy path tests DevFile

• image: maxura/che-server:17194

Tested with Eclipse Che Multiuser User on K8S (minikube v1.1.1)

[skabashnyuk]

ci-build

[skabashnyuk]

[ci-build]