Stats: Merge `stats` interface with `http[s]`

[mkykadir]

Stats interface is also a http[s] interface, before it was required to configure as a separate interface. This change ease configuration of interfaces and still allows configuring stats interface on separate address/port.

Fixes #2888 This changeset also allows us to configure multiple stats interface

If one wants to access stats server from same HTTP interface, following configuration can be used;

interfaces:
    - type: http
       address: 0.0.0.0
       port: 8080
       stats: true

stats server can also be accessed through separate interface with the following configuration;

interfaces:
    - type: http
       address: 0.0.0.0
       port: 8080
    - type: http
       address: 0.0.0.0
       port: 3000
       stats: true

[mkykadir]

Faucet will need an update, reason of Integration test failing

[codecov[bot]]

Codecov Report

Merging #3232 (4774817) into v0.x.x (bda3dfb) will decrease coverage by 1.27%. The diff coverage is 4.76%.

@@            Coverage Diff             @@
##           v0.x.x    #3232      +/-   ##
==========================================
- Coverage   88.64%   87.36%   -1.28%     
==========================================
  Files         167      165       -2     
  Lines       17072    16966     -106     
==========================================
- Hits        15133    14823     -310     
- Misses       1939     2143     +204     

Flag	Coverage Δ
integration	?
unittests	87.36% <4.76%> (-0.03%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
source/agora/node/FullNode.d	72.44% <ø> (-3.01%)	:arrow_down:
source/agora/node/Runner.d	0.00% <0.00%> (-57.36%)	:arrow_down:
source/agora/node/Config.d	69.42% <50.00%> (-11.58%)	:arrow_down:
source/agora/network/RPC.d	1.51% <0.00%> (-59.85%)	:arrow_down:
source/agora/network/VibeManager.d	1.42% <0.00%> (-44.29%)	:arrow_down:
source/agora/network/Clock.d	72.22% <0.00%> (-16.67%)	:arrow_down:
source/scpd/scp/SCPDriver.d	60.00% <0.00%> (-15.00%)	:arrow_down:
source/agora/utils/Log.d	52.20% <0.00%> (-10.07%)	:arrow_down:
... and 8 more

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[Geod24]

My problem with this change is that it forces an http[s] interface. We know that our http[s] interface are more fragile / risky because they go through Vibe.d. That's why it was a separate interface to begin with.

[Geod24]

Reading again, stats is still here, so ignore the above comment.