Reduce ResourceKey's responsibility

[Warashi]

What this PR does:

• move the ResourceKey's method IsDeployment, IsConfigMap, and IsSecret to Manifest's method.

Why we need it:

I want to change ResourceKey's fields, and I want it to have fewer responsibilities.
I want the ResourceKey to be responsible only for identifying the resource.

Which issue(s) this PR fixes:

Part of #4980

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):

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.15%. Comparing base (336d96d) to head (32708fd).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5451      +/-   ##
==========================================
- Coverage   26.16%   26.15%   -0.02%     
==========================================
  Files         456      456              
  Lines       49009    48992      -17     
==========================================
- Hits        12825    12814      -11     
+ Misses      35160    35156       -4     
+ Partials     1024     1022       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[ffjlabo]

LGTM