chore: set library by plugin

[Mercy811]

Revert changes in #174.

Only adding a setting library plugin can update all events including default events' library.

1. Change PUBLISH_VERSION in release.config.js to the latest semantic version
2. build.gradle will then generate BuildConfig.java
3. Set library in FlutterLibraryPlugin

Example BuildConfig.java

/**
 * Automatically generated file. DO NOT MODIFY
 */
package com.amplitude.amplitude_flutter;

public final class BuildConfig {
  public static final boolean DEBUG = Boolean.parseBoolean("true");
  public static final String LIBRARY_PACKAGE_NAME = "com.amplitude.amplitude_flutter";
  public static final String BUILD_TYPE = "debug";
  // Field from default config.
  public static final String SDK_VERSION = "4.0.0-beta.0";
}

Events include default events are set to amplitude-flutter/4.0.0-beta.0
https://app.amplitude.com/analytics/amplitude/project/471621/search/amplitude_id%3D842311306390?sessionHandle=Y38ZXvS_Y38ZXvS_MQdqoyW_BzJF_6ebbafb4-dc1d-4bd7-8ad7-0ff29dceed93R&eventId=98a9598b-1f8f-42a2-924a-20cfcb268b77

[github-actions]

🎉 This PR is included in version 4.0.0-beta.1 🎉

The release is available on GitHub release

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