add a flag to select target types to deregister instance from

[yuxuanzhu0214]

Changes
Added a flag deregister-target-types which is a comma separated list of target types to deregister instance from. By default the value is "classic-elb,target-group". Supported target types are classic-elb and target-group.

Tests
Manually applied the image in dev cluster.

When --deregister-target-types=classic-elb,target-group, life cycle manager scan through all targets that match both target types.

time="2024-08-21T23:21:49Z" level=info msg="i-0ae3409fc1896603a> scanner starting"
time="2024-08-21T23:21:50Z" level=debug msg="cache hit => false, service => elasticloadbalancing.DescribeTargetGroups"
time="2024-08-21T23:21:50Z" level=debug msg="cache hit => false, service => elasticloadbalancing.DescribeLoadBalancers"
time="2024-08-21T23:21:50Z" level=info msg="i-0ae3409fc1896603a> checking targetgroup/elb membership"
time="2024-08-21T23:21:50Z" level=debug msg="len targetgroup: 42, len elb: 1"

When - --deregister-target-types=classic-elb, life cycle manager only scan through targets that are classic elb.

time="2024-08-21T23:08:44Z" level=info msg="i-03fffc250f0ffbe14> scanner starting"
time="2024-08-21T23:08:44Z" level=debug msg="cache hit => true, service => elasticloadbalancing.DescribeLoadBalancers"
time="2024-08-21T23:08:44Z" level=info msg="i-03fffc250f0ffbe14> checking targetgroup/elb membership"
time="2024-08-21T23:08:44Z" level=debug msg="len targetgroup: 0, len elb: 1"

Then life cycle manager deregisters the instance only from targets found from scanning.

[estela-ramirez]

LGTM

[codecov]

Codecov Report

Attention: Patch coverage is 68.75000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 66.72%. Comparing base (ad9b7d7) to head (c80a669).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/service/server.go	68.75%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #214      +/-   ##
==========================================
+ Coverage   66.52%   66.72%   +0.19%     
==========================================
  Files          15       15              
  Lines        1168     1172       +4     
==========================================
+ Hits          777      782       +5     
+ Misses        319      318       -1     
  Partials       72       72              

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