Add plugin planner for k8s

[ffjlabo]

What this PR does / why we need it:

This is an experimental PR for a plugin.
As a first step, I'm trying to convert the k8s planner into the k8s plugin.

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[ffjlabo]

TODO

• how to create gitClient
• how to create secretDecrypter
• fix to get lastSuccessfulConfigFilename from request parameter
• fix to get cfg.Input.HelmChart.Insecur from request parameter
• set version to response

[ffjlabo]

We use piped config passed via grpc request. ref: #4821
Use it to do below ↓

how to create gitClient
how to create secretDecrypter
fix to get lastSuccessfulConfigFilename from request parameter
fix to get cfg.Input.HelmChart.Insecur from request parameter
#4819 (comment)

Also, the set version to response option is not fixed because the version will be deprecated.
https://github.com/pipe-cd/pipecd/blob/master/pkg/model/deployment.pb.go#L257-L258

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 28.91%. Comparing base (930487a) to head (78a070a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4819      +/-   ##
==========================================
+ Coverage   28.88%   28.91%   +0.02%     
==========================================
  Files         317      317              
  Lines       40366    40366              
==========================================
+ Hits        11658    11670      +12     
+ Misses      27779    27767      -12     
  Partials      929      929              

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[ffjlabo]

Current progress: Startup PlannerService as gRPC server.

% cd pkg/app/pipedv1/pluggin/applicationkind/kubernetes
% go run main.go server.go server                                                             
grpc server will be run without tls
grpc server is running on [::]:10000

handled an unary gRPC request: /grpc.pluggin.applicationkind.PlannerService/BuildPlan	{"code": "InvalidArgument", "error": "rpc error: code = InvalidArgument desc = invalid request: invalid BuildPlanRequest.WorkingDir: value length must be at least 1 runes", "duration": 0.000009417}
handled an unary gRPC request: /grpc.pluggin.applicationkind.PlannerService/BuildPlan	{"code": "InvalidArgument", "error": "rpc error: code = InvalidArgument desc = invalid request: invalid BuildPlanRequest.PipedConfig: value length must be at least 1 bytes", "duration": 0.000065375}