Update C++ ISO3DFD readme file

[jkinsky]

Restructured the readme to match new template, rewrote several sections for clarity, and shortened the DevCloud information to make it more concise.

Existing Sample Changes

Description

Restructured the readme to match new template, rewrote several sections for clarity, and shortened the DevCloud information to make it more concise.

Fixes Issue#

External Dependencies

N/A

Type of change

Please delete options that are not relevant. Add a 'X' to the one that is applicable.

• [x] Documentation

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] Command Line
• [x] VSCode

[jkinsky]

@ishaghosh27 please review. @IgorOchocki and @jimmytwei added for notifications.