[Build] Leverage fix env variable matching in maven-toolchains-plugin

[HannesWell]

Since apache/maven-toolchains-plugin#148 is now fixed and the maven-toolchains-plugin version 3.3.0 is about to be released the pipeline can be simplified by removing now unnecessary workarounds.

I've verified this again at the m2e Jenkins instance (https://ci.eclipse.org/m2e/job/try-outs-xtext-Hannes/) using the current RC from:

• https://www.mail-archive.com/dev@maven.apache.org/msg137905.html

Once the vote is completed and the release is published this can be applied and I'll convert this to ready for review.

Additionally I've also considered to remove the strict-jdk-X profiles because at least for the Jenkins use-case they are actually not necessary anymore. However they are also used in the github workflows and can also be useful for local builds if one wants to continue to use the classical approach based on a Maven toolchains.xml file (which can be more convenient for local builds).

[github-actions]

Test Results

  8 054 files  ±0    8 054 suites  ±0   3h 54m 17s ⏱️ + 21m 6s
 43 167 tests ±0   42 583 ✅ ±0    584 💤 ±0  0 ❌ ±0 
212 138 runs  ±0  209 217 ✅ ±0  2 921 💤 ±0  0 ❌ ±0 

Results for commit 9958409. ± Comparison against base commit 3910eb8.

♻️ This comment has been updated with latest results.

[cdietrich]

test ballon with committer rights: https://github.com/eclipse-xtext/xtext/pull/3766/changes

[HannesWell]

Thanks.
The new version is now released and therefore this is ready.

I can rebase the branch tomorrow to retrigger the builds. In case you want at least some green builds on this.

[LorenzoBettini]

All jobs fail due to

[WARNING] The POM for org.apache.maven.plugins:maven-toolchains-plugin:jar:3.3.0 is missing, no dependency information available

cc @HannesWell

[HannesWell]

All jobs fail due to

Rebased the branch now and until now, all builds running well.
Maybe the artifacts needed some time to sync.

[cdietrich]

Thx @HannesWell