Config support for Telemetry service

[tamilmani1989]

…/networkmonitor

2. Added telemetry config through which we can configure reportTohost interval
3. Added unit tests for changes

What this PR does / why we need it:

1. This PR adds support for telemetry service to read config file which provides a way to configure time interval for sending telemetry payload to host
2. Moved telemetry specific functions to telemetry package so that other components can use
3. Start telemetry process with argument which indicates config directory ( eg: azure-vnet-telemetry -d <dir_path>). By default it will look for config in /opt/cni/bin.
4. Moved log initialization in telemetry service process code.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:
Run unit tests for linux and windows. Did sanity testing in linux and windows. For multitenancy, requires changes in cns/dnc which will be a separate PR

Release note:

[codecov]

Codecov Report

Merging #317 into master will increase coverage by 0.8%.
The diff coverage is 64.1%.

@@            Coverage Diff            @@
##           master     #317     +/-   ##
=========================================
+ Coverage   45.71%   46.51%   +0.8%     
=========================================
  Files          25       25             
  Lines        3478     3433     -45     
=========================================
+ Hits         1590     1597      +7     
+ Misses       1634     1587     -47     
+ Partials      254      249      -5

Impacted Files	Coverage Δ
telemetry/telemetry.go	29.41% <0%> (ø)	⬆️
telemetry/telemetrybuffer.go	57.37% <65.78%> (-0.69%)	⬇️
npm/pod.go	62.62% <0%> (+0.77%)	⬆️
npm/namespace.go	59.43% <0%> (+0.78%)	⬆️
npm/nwpolicy.go	56.09% <0%> (+1.09%)	⬆️
npm/iptm/iptm.go	56.33% <0%> (+1.45%)	⬆️
telemetry/telemetrybuffer_linux.go	87.5% <0%> (+6.25%)	⬆️
npm/npm.go	10.28% <0%> (+8.13%)	⬆️

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[jaer-tsun]

lgtm