Improve the Zowe V2 install doc by adding install diagram

[nannanli]

Is your request for enhancement related to a problem? Please describe.

The Zowe installation doc contains many details and steps. It's easy to get lost in various topics, details and links while following the docs to install and configure Zowe.

Describe the solution you'd like

The Zowe installation roadmap diagram is found to be helpful.

• it would be good if there is a checklist of all the steps that must be complete, especially for complex tasks such as configuring certificates
• The Zowe installation roadmap could be more obvious even as the first topic for installation to give an overview first. Currently it's placed after the planning topic but the planning section.
• Would be good to know how long a particular step will take.
• How many space zowe will require for the install.
• More screen captures would be helpful. For example in the case of slash for SDSF commands.

Related doc pages

https://docs.zowe.org/stable/user-guide/install-zos.html

Additional context