Rename --project_id to --bes_instance_name

This makes it clearer that this flag affects the BES and not, e.g.,
remote cache or execution. `--bes_instance_name` was chosen to match
`--remote_instance_name` as closely as possible.

`--project_id` always seemed very Google/GCP centric, and now that
there are multiple other BES implementations like BuildBuddy or EngFlow
Build and Test UI, it makes sense to change the terminology to follow
the conventions from the REAPI. We will keep `--project_id` as an alias
for the foreseable future.

Closes bazelbuild#14455.

PiperOrigin-RevId: 418972581

Author: Yannic

src/main/java/com/google/devtools/build/lib/buildeventservice/BuildEventServiceModule.java

@@ -692,7 +692,7 @@ private BuildEventServiceTransport createBesTransport(
         new BuildEventServiceProtoUtil.Builder()
             .buildRequestId(buildRequestId)
             .invocationId(invocationId)
-            .projectId(besOptions.projectId)
+            .projectId(besOptions.instanceName)
             .commandName(cmdEnv.getCommandName())
             .keywords(getBesKeywords(besOptions, cmdEnv.getRuntime().getStartupOptionsProvider()))
             .build();

src/main/java/com/google/devtools/build/lib/buildeventservice/BuildEventServiceOptions.java

@@ -88,13 +88,15 @@ public class BuildEventServiceOptions extends OptionsBase {
   public boolean besLifecycleEvents;
 
   @Option(
-    name = "project_id",
-    defaultValue = "null",
-    documentationCategory = OptionDocumentationCategory.LOGGING,
-    effectTags = {OptionEffectTag.AFFECTS_OUTPUTS},
-    help = "Specifies the BES project identifier. Defaults to null."
-  )
-  public String projectId;
+      name = "bes_instance_name",
+      oldName = "project_id",
+      defaultValue = "null",
+      documentationCategory = OptionDocumentationCategory.LOGGING,
+      effectTags = {OptionEffectTag.AFFECTS_OUTPUTS},
+      help =
+          "Specifies the instance name under which the BES will persist uploaded BEP. Defaults "
+              + "to null.")
+  public String instanceName;
 
   @Option(
       name = "bes_keywords",