Implement checkImageChange and tests

[Warashi]

What this PR does:

Implement checkImageChange and tests.
The checkImageChange detects changed images from the difference of manifests.

Why we need it:

We must detect whether there are changed images or not to determine the sync strategy and its descriptions.
If there are changed images in diffs, we choose the pipeline sync strategy.
If there are no changed images in diffs, we determine the sync strategy with other viewpoints.

Which issue(s) this PR fixes:

Part of #4980

Does this PR introduce a user-facing change?: No

• 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 25.31%. Comparing base (1763f92) to head (1112cd9).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5333      +/-   ##
==========================================
+ Coverage   25.28%   25.31%   +0.02%     
==========================================
  Files         444      444              
  Lines       47574    47592      +18     
==========================================
+ Hits        12028    12046      +18     
  Misses      34603    34603              
  Partials      943      943              

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[khanhtc1202]

nits, Could you add a test case to show that the order of the image matters to this checkImageChange function 👀

{
			name: "change the order cause multi-image update",
			old: `
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-deployment
spec:
  template:
    spec:
      containers:
      - name: nginx
        image: nginx:1.19.3
      - name: redis
        image: redis:6.0.9
`,
			new: `
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-deployment
spec:
  template:
    spec:
      containers:
      - name: redis
        image: redis:6.0.9
      - name: nginx
        image: nginx:1.19.3
`,
			want:   "Sync progressively because of updating image nginx:1.19.3 to redis:6.0.9, image redis:6.0.9 to nginx:1.19.3",
			wantOk: true,
		},

[Warashi]

Thanks. I added it on this commit.
1112cd9

[khanhtc1202]

LGTM with small nits 👍

[khanhtc1202]

LGTM

[ffjlabo]

LGTM