[Analytics] Editor sessions do not report classic blocks as unsupported

[guarani]

Describe the bug

Tracks analytics don't detect classic blocks when reporting posts events (editor_session_start and editor_session_end). Editing a post (in the block editor) that contains classic blocks should result in a tracks event where has_unsupported_blocks is 1. Instead what I see on both platforms for both these events is a has_unsupported_blocks of value 0.

Posts containing other unsupported blocks (e.g. Jetpack timeline blocks) appear to have the correct has_unsupported_blocks value.

To Reproduce

1. Create a post on the web and add a classic block, then add some content to it and publish it
2. To test on WPiOS:
   a. Run WPiOS in Xcode
   b. Open the debug console (View > Debug Area > Activate Console)
   c. Optionally add 🔵 Tracked: editor_ to the console filter to filter out unwanted events
   d. Open the post created in Step 1
   e. Observe the editor_session_start event's has_unsupported_blocks property has a value of 0 (I expected to see 1)
   f. Close the editor
   g. Observe the editor_session_end event's has_unsupported_blocks property has a value of 0 (I expected to see 1)
3. Similar steps work to test this on WPAndroid

Expected behavior
I expected classic blocks to be reported as unsupported blocks. Even though they are not traditional Gutenberg blocks, they are editable in the Unsupported Block Editor and I think for analytics purposes we would also expect them to be reported just like any other block.

Smartphone (please complete the following information):

• Device: iPhone simulator / Android emulator
• OS: iOS 14.4.2 or Android 10
• Version develop branches of both repos

Additional context

This issue was discovered while investigating #3228 but is not the the same issue. #3228 is iOS-specific and only the editor_session_start event is affected, while this issue was seen on both WPiOS and WPAndroid on both these events.