[Toolbox] Hot Reloading breaks SingleModulePlugin

[jasonLaster]

We recently introduced SingleModulePlugin to help with issues where two modules would require the same module, but get different closure scopes: e.g.

• toolbox / main would get a different clientType
• networkRequest did not get the config when it was set in source-map-worker

This broke hotReloading because SMP relies on a string comparison of the modules to determine similarity and HR injected a react dependency with a different module id.

We'll fix this soon by stripping HR injected lines from the comparison

CC @juliandescottes

[jasonLaster]

Fixed!