SC reorg & expand: data, tooling, config

[andrei-marinica]

Description of the pull request (what is new / what has changed)

Major reorganization and expansion of a few sections:

• Serialization format:
  • expanded to a new section
  • split existing page into Simple Values, Composite Values, Custom Types, Defaults
  • added ABI docs
  • added multi-value docs
  • code metadata moved here
• New Configuration & Tooling section
  • moved build CLI to new CLI specs page
  • new CLI specs for the standalone tool
  • new allocator page, adapted from release notes
  • reorganized build reference
  • new descriptions of tools: test-gen, update, template

Did you test the changes locally ?

• yes
• no

Which category (categories) does this pull request belong to?

• document new feature
• update documentation that is not relevant anymore
• add examples or more information about a component
• fix grammar issues
• other