Draft: Sanity check build with JDK 18 on CI

[szpak]

Add basic JDK 18 tests on CI with Temurin.

Unfortunately, Gradle 7.4.1/2 refuses to play with JDK 18:

 * What went wrong:
A problem occurred evaluating project ':spock-specs'.
> Could not resolve all dependencies for configuration ':spock-specs:jacocoAgentRuntime'.
   > Failed to query the value of task ':spock-specs:compileGroovy' property 'javaLauncher'.
      > No compatible toolchains found for request filter: {languageVersion=18, vendor=any, implementation=vendor-specific} (auto-detect true, auto-download false)

However, it builds fine locally with JDK 18. Is it "just" a toolchain detection issue which could be easily overridden or Gradle 7.5 is a must?

[codecov[bot]]

Codecov Report

Merging #1457 (00b5e4d) into master (7fa3d62) will increase coverage by 0.00%. The diff coverage is n/a.

:exclamation: Current head 00b5e4d differs from pull request most recent head f65b7b9. Consider uploading reports for the commit f65b7b9 to get more accurate results

@@            Coverage Diff            @@
##             master    #1457   +/-   ##
=========================================
  Coverage     79.59%   79.59%           
+ Complexity     4010     4005    -5     
=========================================
  Files           404      404           
  Lines         12563    12562    -1     
  Branches       1641     1640    -1     
=========================================
  Hits           9999     9999           
- Misses         1969     1971    +2     
+ Partials        595      592    -3     

Impacted Files	Coverage Δ
...main/java/org/spockframework/compiler/AstUtil.java	79.57% <0.00%> (-0.71%)	:arrow_down:
...java/org/spockframework/compiler/SpecRewriter.java	93.69% <0.00%> (-0.02%)	:arrow_down:
.../spockframework/gentyref/GenericTypeReflector.java	35.23% <0.00%> (ø)
...rg/spockframework/runtime/MasterRunSupervisor.java	82.25% <0.00%> (+1.61%)	:arrow_up:
.../main/java/org/spockframework/gentyref/VarMap.java	74.19% <0.00%> (+3.22%)	:arrow_up:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 7fa3d62...f65b7b9. Read the comment docs.

[szpak]

While the toolchain is fixed, one test fails with JDK18 (Temurin 18.0.1+10) on CI: https://github.com/spockframework/spock/runs/6235781892?check_suite_focus=true#step:4:141

PartialMockingInterfacesWithDefaultMethods > IQuarterlyCompoundedDeposit: should throw unchecked exception for negative values of principalAmount FAILED
    Expected exception of type 'java.lang.IllegalArgumentException', but got 'java.lang.reflect.UndeclaredThrowableException'

but locally everything passes with JDK 18 (OpenJDK 18+37 by RedHat)...

[Vampire]

As we have test run for Java 21 now, this PR is obsolete, isn't it?