switch build agent terminology in user-facing documentation

src/main/java/org/jenkinsci/plugins/workflow/steps/durable_task/ShellStep.java

@@ -36,7 +36,7 @@
 import java.util.Map;
 
 /**
- * Runs a Bourne shell script asynchronously on a slave.
+ * Runs a Bourne shell script asynchronously on a build agent.
  */
 public final class ShellStep extends DurableTaskStep {
 

src/main/java/org/jenkinsci/plugins/workflow/support/steps/ExecutorStep.java

@@ -59,7 +59,7 @@
  * Used like:
  * <pre>
  *     node("foo") {
- *         // execute some stuff in a slave that has a label "foo" while workflow has this slave
+ *         // execute some stuff in a build agent that has a label "foo" while workflow has this build agent
  *     }
  * </pre>
  */

src/main/java/org/jenkinsci/plugins/workflow/support/steps/ExecutorStepExecution.java

@@ -773,7 +773,7 @@ private static final class Callback extends BodyExecutionCallback.TailCall {
         }
 
         /**
-         * Occupies {@link Executor} while workflow uses this slave.
+         * Occupies {@link Executor} while workflow uses this build agent.
          */
         @ExportedBean
         private final class PlaceholderExecutable implements ContinuableExecutable, AccessControlled {

src/main/resources/index.jelly

@@ -25,5 +25,5 @@ THE SOFTWARE.
 
 <?jelly escape-by-default='true'?>
 <div>
-    Pipeline steps locking agents and workspaces, and running external processes that may survive a Jenkins restart or slave reconnection.
+    Pipeline steps locking agents and workspaces, and running external processes that may survive a Jenkins restart or agent reconnection.
 </div>

src/main/resources/org/jenkinsci/plugins/workflow/support/steps/ExecutorStep/help.html

@@ -1,3 +1,3 @@
 <div>
-    Allocates an executor on a node (typically a slave) and runs further code in the context of a workspace on that slave.
+    Allocates an executor on a node (typically a build agent) and runs further code in the context of a workspace on that agent.
 </div>

src/main/resources/org/jenkinsci/plugins/workflow/support/steps/WorkspaceStep/help-dir.html

@@ -2,11 +2,11 @@
     A workspace is automatically allocated for you with the <code>node</code> step,
     or you can get an alternate workspace with this <code>ws</code> step,
     but by default the location is chosen automatically.
-    (Something like <code>SLAVE_ROOT/workspace/JOB_NAME@2</code>.)
+    (Something like <code>AGENT_ROOT/workspace/JOB_NAME@2</code>.)
 </p>
 <p>
     You can instead specify a path here and that workspace will be locked instead.
-    (The path may be relative to the slave root, or absolute.)
+    (The path may be relative to the build agent root, or absolute.)
 </p>
 <p>
     If concurrent builds ask for the same workspace, a directory with a suffix such as <code>@2</code> may be locked instead.

src/test/java/org/jenkinsci/plugins/workflow/support/steps/ExecutorStepTest.java

@@ -136,7 +136,7 @@ public class ExecutorStepTest {
     @Rule public LoggerRule logging = new LoggerRule();
 
     /**
-     * Executes a shell script build on a slave.
+     * Executes a shell script build on a build agent.
      *
      * This ensures that the context variable overrides are working as expected, and
      * that they are persisted and resurrected.
@@ -183,7 +183,7 @@ public class ExecutorStepTest {
     }
 
     /**
-     * Executes a shell script build on a slave and ensures the processes are
+     * Executes a shell script build on a build agent and ensures the processes are
      * killed at the end of the run
      *
      * This ensures that the context variable overrides are working as expected, and