Plugin's tasks ignore configured java toolchain

[fzhinkin]

kotlinx-benchmarks tasks responsible for compiling and running benchmarks on JVM ignore a toolchain configured for a project and instead use the same JDK as Gradle do.

That to leads to compilation failures when a project is configured to use a toolchain that is newer than the java Gradle was launched with.

For example, a project's toolchain is JDK 21, but Gradle was started with JDK 17:

Execution failed for task ':kotlinx-io-benchmarks:jvmBenchmarkGenerate'.
> There was a failure while executing work items
   > A failure occurred while executing kotlinx.benchmark.gradle.JmhBytecodeGeneratorWorker
      > kotlinx/io/benchmarks/ShortBenchmark has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 61.0

It would be nice to align kotlinx-benchmarks' tasks behavior with Kotlin Gradle plugins and use JDK configured using toolchains.

[fzhinkin]

Related feature that would be nice to support (but it probably deserves a separate issue): allow configuring different toolchains for different benchmarks configurations, so that a user could execute the same set of benchmarks with different JDK versions. Something like:

configurations {
    create("jdk17") {
        mode = "avgt"
        outputTimeUnit = "ns"
        include("MyPreciousBenchmark")
        jvmToolchain {
            languageVersion.set(JavaLanguageVersion.of(17))
        }
    }
    create("jdk21") {
        mode = "avgt"
        outputTimeUnit = "ns"
        include("MyPreciousBenchmark")
        jvmToolchain {
            languageVersion.set(JavaLanguageVersion.of(21))
        }
    }
}

[fzhinkin]

Filed #187 to track #176 (comment)