[Document] Apply design template to flow diagram

[kevindiu]

Description:

This PR update the design of the flow diagram on the architecture document.

Related Issue:

How Has This Been Tested?:

Environment:

• Golang Version: 1.14.3
• Docker Version: 19.03.8
• Kubernetes Version: 1.18.2
• NGT Version: 1.11.5

Types of changes:

• Bug fix [type/bug]
• New feature [type/feature]
• Add tests [type/test]
• Security related changes [type/security]
• Add documents [type/documentation]
• Refactoring [type/refactoring]
• Update dependencies [type/dependency]
• Update benchmarks and performances [type/bench]
• Update CI [type/ci]

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

Checklist:

• I have read the CONTRIBUTING document.
• I have checked open Pull Requests for the similar feature or fixes?
• I have added tests and benchmarks to cover my changes.
• I have ensured all new and existing tests passed.
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly.

[pull-assistant]

Best reviewed: commit by commit

---

Optimal code review plan

     apply template to flow diagram

     update flow description

     update images

     update diagrams

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[hlts2]

LGTM

[kevindiu]

/rebase

[vdaas-ci]

[REBASE] Rebase triggered by kevindiu for branch: documentation/update_arch_diagram

edit test: rinx

[hlts2]

LGTM

[vankichi]

LGTM
/approve
/rebase
/approve