Some extension subcategories can go missing

Problem

Loading an extension and then loading a second extension that contains the first can lead to missing subcategories.

Repro Steps

1. Open up a Microbit and reset the page or clear the __pxt_apis_microbit indexed db entry.
2. Start a new project and load the makerbit-lcd1602 extension. You'll see a MakerBit category in the toolbox with LCD1602 and LCD2004 subcategories under it.
3. Load the makerbit extension, which includes the same lcd1602 code. You'll now see that the LCD2004 category is gone while the LCD1602 category remains.

If you look for 2004 in the toolbox search bar, you'll still be able to find the LCD2004 blocks.

Expected Behavior

The expected behavior is that the LCD2004 subcategory should not disappear.

Note

The problem probably lies with how namespaces for extensions are defined.

After Loading Just the makerbit-lcd1602 extension

After loading the makerbit extension as well

Searching for the LCD2004 blocks

Desktop:

• OS: Windows 10 1909
• Browser Microsoft Edge v. 86.0.622.56
• makecode.microbit.org version: 3.0.43
• Microsoft MakeCode version: 6.0.28
• microbit runtime version: v2.2.0-rc6

Additional context

Refer to #7562 for additional context.

Reproduce the issue on the Microbit target by loading makerbit-lcd1602, then makerbit, and compare the toolbox categories with the toolbox search results. Start by tracing how extension namespaces and toolbox subcategories are defined and merged; issue #7562 provides additional context. Done means LCD2004 remains visible after both extensions are loaded.