Ensure `rootProject.name` is only set from `settings.gradle`

I moved this assignment in https://github.com/google/ExoPlayer/commit/326f53a61c4e58a9123561e0f0c838c40929852f
in order to provide a single source-of-truth for `publish.gradle`,
but as pointed out in Issue: androidx/media#416 this breaks apps that are depending
on our project locally using the instructions we publish. Instead we can
remove the `rootProject.name` check from `publish.gradle`, and check an
explicit boolean value instead to indicate if the root project is 'ours'
(with this boolean only set from `settings.gradle`, so it doesn't get
picked up by apps depending on us locally).

#minor-release

PiperOrigin-RevId: 534459085
(cherry picked from commit 3ca3e11de1ab7c8a1fde0f9dd92dd9724fedcc56)

core_settings.gradle

@@ -21,8 +21,6 @@ def modulePrefix = ':'
      modulePrefix += gradle.ext.exoplayerModulePrefix
  }
 
- rootProject.name = 'exoplayer2'
-
 include modulePrefix + 'library-common'
 project(modulePrefix + 'library-common').projectDir = new File(rootDir, 'library/common')
 

settings.gradle

@@ -18,6 +18,8 @@ def modulePrefix = ':'
      modulePrefix += gradle.ext.exoplayerModulePrefix
  }
 
+ rootProject.name = 'exoplayer2'
+
 include modulePrefix + 'demo'
 project(modulePrefix + 'demo').projectDir = new File(rootDir, 'demos/main')
 include modulePrefix + 'demo-cast'