Prevent WASM from crashing on startup when using FpsOverlayPlugin

[it-me-joda]

Objective

• Fixes FrameTimeGraph, even disabled, crashes wasm on load (FrametimeGraphMaterial) #21362
• The FrameTimeGraph uses a material that crashes in WASM even if the FrameTimeGraph is disabled. We need to prevent the FrameTimeGraph from being created when we build for WASM.

Solution

• If the build is for WASM, we skip the ceration of the FrameTimeGraph. Additionally, if the FrameTimeGraph is enabled, we provide a warning to inform the user that the FrameTimeGraph isn't supported on WASM.

Testing

• I used the repro provided in the issue.