fix: Update SystemExecutors to only use 4 threads, always (#1209)

This can cause contention issues on high-core-count machines Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly: - [ ] Make sure to open an issue as a [bug/issue](https://github.com/googleapis/java-pubsublite/issues/new/choose) before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea - [ ] Ensure the tests and linter pass - [ ] Code coverage does not decrease (if any source code was changed) - [ ] Appropriate docs were updated (if necessary) Fixes #<issue_number_goes_here> ☕️ If you write sample code, please follow the [samples format]( https://github.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).

Author: dpcollins-google

README.md

@@ -32,13 +32,13 @@ If you are using Maven, add this to your pom.xml file:
 If you are using Gradle without BOM, add this to your dependencies:
 
 ```Groovy
-implementation 'com.google.cloud:google-cloud-pubsublite:1.6.3'
+implementation 'com.google.cloud:google-cloud-pubsublite:1.7.0'
 ```
 
 If you are using SBT, add this to your dependencies:
 
 ```Scala
-libraryDependencies += "com.google.cloud" % "google-cloud-pubsublite" % "1.6.3"
+libraryDependencies += "com.google.cloud" % "google-cloud-pubsublite" % "1.7.0"
 ```
 
 ## Authentication

google-cloud-pubsublite/src/main/java/com/google/cloud/pubsublite/internal/wire/SystemExecutors.java

@@ -33,9 +33,7 @@ private static ThreadFactory newDaemonThreadFactory(String prefix) {
 
  public static ScheduledExecutorService newDaemonExecutor(String prefix) {
  ScheduledThreadPoolExecutor executor =
- new ScheduledThreadPoolExecutor(
- Math.max(4, Runtime.getRuntime().availableProcessors()),
- newDaemonThreadFactory(prefix));
+ new ScheduledThreadPoolExecutor(4, newDaemonThreadFactory(prefix));
  // Remove scheduled tasks from the executor as soon as they are cancelled.
  executor.setRemoveOnCancelPolicy(true);
  return executor;