src: allow preventing InitializeInspector in env

[codebytere]

This PR adds a new EnvironmentFlags option: kNoInitializeInspector.

8c5ad13 made it such that env->InitializeInspector was called in CreateEnvironment
no matter what, which creates an issue for embedders seeking to manage the InspectorAgent themselves as Electron does. This new flag mitigates that issue by allowing embedders to prevent that invocation.

cc @joyeecheung

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines