Ensure test temporary directory exists (#52227)

Today we we set the test temporary directory explicitly by controling
java.io.tmpdir. Yet, we do not guarantee this directory exists, instead
relying on a test base class (LuceneTestCase) to create this directory
when it initializes. However, some of our tests do not rely on our test
framework, and thus do not have access to LuceneTestCase, instead
relying on RandomizedRunner directly. We should not be relying on the
temporary directory being implicitly created, instead guaranteeing that
it exists before test execution starts. This commit does that by
creating the test temporary directory before the test task executes (via
a doFirst).

buildSrc/src/main/groovy/org/elasticsearch/gradle/BuildPlugin.groovy

@@ -694,6 +694,7 @@ class BuildPlugin implements Plugin<Project> {
                     project.mkdir(testOutputDir)
                     project.mkdir(heapdumpDir)
                     project.mkdir(test.workingDir)
+                    project.mkdir(test.workingDir.toPath().resolve('temp'))
 
                     if (BuildParams.runtimeJavaVersion >= JavaVersion.VERSION_1_9) {
                         test.jvmArgs '--illegal-access=warn'