Add Timeouts functionality

[italolelis]

What does this PR do?

• Improves the Makefile
• Removes the -race flag from tests as this breaks on alpine, this is golang issue
• Removes the enable_load_balancing property which was not used
• Removes the ReadOnly configuration for the admin API
• Removes the Debug configuration from the configuration as this was not used
• Makes the transport layer less smart and leave the stats tracking to the stats middleware
• Moves the balancer logic to its own package
• Adds an alias for the roundrobin load balancing which is called rr
• Adds request and server timeouts and solves #320. Now we'll be able to configure timeouts per endpoits as well as timeouts for Janus server. Everything comes with defaults so this should not affect productions servers at HelloFresh. The new configurations are:

For Janus server:

#[respondingTimeouts]
# readTimeout is the maximum duration for reading the entire request, including the body.
#
# Optional
# Default: "0s"
#
# readTimeout = "5s"

# writeTimeout is the maximum duration before timing out writes of the response.
#
# Optional
# Default: "0s"
#
# writeTimeout = "5s"

# idleTimeout is the maximum duration an idle (keep-alive) connection will remain idle before closing itself.
#
# Optional
# Default: "180s"
#
# idleTimeout = "360s"

Per endpoint:

{
"forwarding_timeouts": {"dial_timeout": "30s", "response_header_timeout": "60s"} 
}

[codecov[bot]]

Codecov Report

Merging #323 into master will increase coverage by 1.02%. The diff coverage is 39.47%.

@@            Coverage Diff             @@
##           master     #323      +/-   ##
==========================================
+ Coverage   40.72%   41.75%   +1.02%     
==========================================
  Files          72       74       +2     
  Lines        2512     2467      -45     
==========================================
+ Hits         1023     1030       +7     
+ Misses       1427     1376      -51     
+ Partials       62       61       -1

Impacted Files	Coverage Δ
pkg/web/provider.go	0% <ø> (ø)	:arrow_up:
pkg/web/options.go	0% <ø> (ø)	:arrow_up:
pkg/plugin/oauth2/oauth_introspection.go	0% <0%> (ø)	:arrow_up:
pkg/plugin/oauth2/setup.go	7.86% <0%> (ø)	:arrow_up:
pkg/proxy/register_options.go	0% <0%> (ø)
pkg/proxy/register.go	0% <0%> (ø)	:arrow_up:
pkg/proxy/reverse_proxy.go	0% <0%> (ø)
pkg/plugin/oauth2/loader.go	0% <0%> (ø)	:arrow_up:
pkg/plugin/cors/setup.go	88.88% <100%> (ø)	:arrow_up:
pkg/plugin/responsetransformer/middleware.go	100% <100%> (ø)	:arrow_up:
... and 19 more

---

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Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update f3b78ab...2a434db. Read the comment docs.

[vgarvardt]

@italolelis can you pls split this PR into 2 or 3 to make changes more granular and review a bit easier?

E.g. extract -race, enable_load_balancing and Debug related changes into the first PR, balancing changes/refactoring into another and Timeout functionality into the third one.

[italolelis]

@vgarvardt The timeouts and balancer transport refactors have to be on the same PR, they are dependent. I could split the race stuff but they are tiny, that's why they are in the same PR. If you want I can split the -race, enable_load_balancing and Debug but not the other two