Add a way to disable admin profiler

[reclaro]

This change adds a way to disable the admin profiler when the admin
server is enabled.

I added a new env variable that can be used to disable the admin profiler
To verify it you can:

• Enable the admin api
• set the "FN_ENABLE_ADMIN_PROFILER" to "false"
• GET the admin_api:admin_port/debug/vars, you should get an error

[rdallman]

this seems like a really weird concern? are there issues with having admin authentication guarding these endpoints to begin with? - that seems like the real issue, no admin should reasonably be worried about this?

[reclaro]

Hey @rdallman thanks for your comment, this is not a big deal i am happy to abandon this change if we think there is no value, the reason because I am proposing this is that we can have some FN implementations where different profiling mechanism are plugged into the system and therefore the net/http/pprof won't be necessary and ppl want a way to switch it off.

[reclaro]

working on this thing I noticed that we don't call the wrapper for injecting middleware in the Admin API, I opened a PR for this #1327

[rdallman]

@reclaro i think that #1327 is the right path forward here, thanks for following up

[reclaro]

Ok I close this ticket in favor of #1327