[regression] after the debugger change, graph plugin always show health pill

When graph plugin loads, it can make requests1 to the debugger routes which is not always provided by all possible implementations of the debugger_plugin 2.

It causes random JavaScript exceptions like below which is quite noisy:

POST http://localhost:6006/data/plugin/debugger/health_pills 404 (NOT FOUND)
Show 130 more frames
(index):17958 GET http://localhost:6006/data/plugin/debugger/numerics_alert_report 404 (NOT FOUND)
Show 130 more frames
(index):17958 POST http://localhost:6006/data/plugin/debugger/health_pills 404 (NOT FOUND)

I was able to bisect and, indeed, after dacf300259f850740424a1c228d0a693cffda548, we started to see below.