[WIP] Benchpark New Developer Docs

[amroakmal]

Based on what I learned and my understanding so far, this issue tracks new insights into Benchpark (BP) to deepen understanding of its execution flow. It also serves as developer documentation by offering more detailed information than the main docs.

Fixes: #785

Summary for what's introduced:

1. Introduce Developer Documentation that are more in depth than default docs, for discussing some important Benchpark concepts (e.g. variants, modifiers)
2. Deeper details for what core BP commands make upon execution
3. Easy steps for debugging BP with VSCode providing the launch configurations
4. Easier installation for dependencies needed for building the docs/ to be able to check locally

[pearce8]

Please fix the spelling which makes docs build fail.

[amroakmal]

Please fix the spelling which makes docs build fail.

@pearce8 : Done, Dr. Olga, and rebased too.

[michaelmckinsey1]

Some content review and suggestions

[michaelmckinsey1]

I would advise to split

* `Core Concepts and Patterns`_ - Understanding Variants, Consistent Flow, and Modifiers
* `Benchpark Command Workflow`_ - Step-by-step execution of key Benchpark commands  
* `Debugging Benchpark with VSCode`_ - Setting up debugging environment for development

these into 3 pages here instead of 1 single page.