add a way to set the java compiler version in the gradle build

[daymonro]

No description provided.

[Copilot]

Pull Request Overview

This PR adds flexibility to the Java compiler version configuration in the Gradle build system by allowing it to be set via system properties or environment variables, rather than being hardcoded to Java 11.

Key Changes:

• Introduces a configurable Java version mechanism with multiple configuration sources (system property, environment variable, or default fallback)
• Replaces the hardcoded Java 11 version with a dynamic version resolution system

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[Copilot]

The conversion chain .get().toInteger() could fail with unclear errors if a non-numeric value is provided. Consider using .map { Integer.parseInt(it) } before the final assignment to provide better error handling, or add validation to ensure the value is numeric before conversion.

Suggested change

	languageVersion = JavaLanguageVersion.of(requestedVersion.get().toInteger())
	languageVersion = JavaLanguageVersion.of(requestedVersion.map {
	try {
	Integer.parseInt(it)
	} catch (NumberFormatException e) {
	throw new GradleException("Invalid javaVersion/JAVA_VERSION: '$it' is not a valid integer")
	}
	}.get())