[Spike] Investigate flagging dynamic styles passed to `css` prop

[weronikaolejniczak]

The purpose of this spike is to investigate how to flag dynamic styles passed to css prop.

Options

1. Monkey patch insert function. We can do it through our EuiProvider, overriding cache.insert function. We can keep a map of styles and on having inserted the same style again, we can verify whether the saved value is the same as serialized.styles. If not, we can flag it as a dynamic style. PoC
2. ...

Acceptance criteria

• [ ] Different options are considered and added to the "Options" section
• [ ] PoC and / or documentation is created around each option's advantages, disadvantages, feasibility and limitations