Revert "[ai-completion] LLM-16065: store MLCompletionSession per editor inside InlineCompletionRequest"

This reverts commit a4409cdf8c815b2531af73fb0d9a27f20e3ad0af.

GitOrigin-RevId: 77f3da135457ed721b835240a90aa7329bc247ef

Author: Petr Surkov

platform/platform-impl/codeinsight-inline/src/com/intellij/codeInsight/inline/completion/session/InlineCompletionContext.kt

@@ -20,8 +20,7 @@ class InlineCompletionContext internal constructor(
   /**
    * @see dispose
    */
-  @Volatile
-  var isDisposed: Boolean = false
+  var isDisposed = false
     @RequiresEdt
     get
     private set

platform/platform-impl/codeinsight-inline/src/com/intellij/codeInsight/inline/completion/session/InlineCompletionSession.kt

@@ -171,6 +171,7 @@ class InlineCompletionSession private constructor(
     private val LOG = thisLogger()
     private val INLINE_COMPLETION_SESSION = Key.create<InlineCompletionSession>("inline.completion.session")
 
+    @RequiresEdt
     fun getOrNull(editor: Editor): InlineCompletionSession? = editor.getUserData(INLINE_COMPLETION_SESSION)
 
     @RequiresEdt