Fix directory separator in ProcessResource attributes (open-telemetry…

…#6716)

The separator char used to build the Java executable path in
ProcessResource is wrong: `File.pathSeparatorChar` is the PATH variable
separator (`:` on Linux, `;` on Windows), the right one for directories
is `File.separatorChar` (`/` on Linux, `\` on Windows).

Note that this issue was already present in
[sdk-extensions-resources](https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/resources/src/main/java/io/opentelemetry/sdk/extension/resources/ProcessResource.java#L64)
before it was moved here; should it be fixed there too?

instrumentation/resources/library/src/main/java/io/opentelemetry/instrumentation/resources/ProcessResource.java

@@ -61,9 +61,9 @@ private static Resource doBuildResource() {
     if (javaHome != null) {
       StringBuilder executablePath = new StringBuilder(javaHome);
       executablePath
-          .append(File.pathSeparatorChar)
+          .append(File.separatorChar)
           .append("bin")
-          .append(File.pathSeparatorChar)
+          .append(File.separatorChar)
           .append("java");
       if (osName != null && osName.toLowerCase().startsWith("windows")) {
         executablePath.append(".exe");

instrumentation/resources/library/src/test/java/io/opentelemetry/instrumentation/resources/ProcessResourceTest.java

@@ -28,9 +28,7 @@ void notWindows() {
     Attributes attributes = resource.getAttributes();
 
     assertThat(attributes.get(ResourceAttributes.PROCESS_PID)).isGreaterThan(1);
-    assertThat(attributes.get(ResourceAttributes.PROCESS_EXECUTABLE_PATH))
-        .contains("java")
-        .doesNotEndWith(".exe");
+    assertThat(attributes.get(ResourceAttributes.PROCESS_EXECUTABLE_PATH)).matches(".*[/\\\\]java");
     assertThat(attributes.get(ResourceAttributes.PROCESS_COMMAND_LINE))
         .contains(attributes.get(ResourceAttributes.PROCESS_EXECUTABLE_PATH));
   }
@@ -44,8 +42,7 @@ void windows() {
 
     assertThat(attributes.get(ResourceAttributes.PROCESS_PID)).isGreaterThan(1);
     assertThat(attributes.get(ResourceAttributes.PROCESS_EXECUTABLE_PATH))
-        .contains("java")
-        .endsWith(".exe");
+        .matches(".*[/\\\\]java\\.exe");
     assertThat(attributes.get(ResourceAttributes.PROCESS_COMMAND_LINE))
         .contains(attributes.get(ResourceAttributes.PROCESS_EXECUTABLE_PATH));
   }