"setTheme" gets called every time a new instance of Editor is initialised

[saikatmitra91]

Describe the bug
My app contains multiple instances of Editor some of which load dynamically.
Every time a new editor is initialised the theme gets set again causing a flash in all the other initialised editor instances as well.

To Reproduce

Steps to reproduce the behavior:

1. Go to https://www.empirical.run/gpt-3-5-turbo-vs-gpt-4
2. Click on one of the "Schema" buttons
3. Look at the cells closely. The currently drawn cells flash while the schema drawer opens.

[suren-atoyan]

This issue should be addressed to microsoft/monaco-editor.

There is already one