[EUI+] Reorganise the document pages

[weronikaolejniczak]

The purpose of this task is to reorganize some document pages to allow for easier navigation and information discovery.

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Run the new docs locally (go through the steps in the README.md file) or use some staging environment.

Sub-tasks:

• [ ] Move Components > Elastic Charts to top-level Data Visualization section
• [ ] Split up Button component into different subpages for EuiButtonEmpty, EuiButtonIcon, and EuiButtonGroup
• [ ] Split out EuiFlyoutResizable to a sub-page of EuiFlyout (+ move props table)
• [ ] Split out EuiTable* subcomponents to a sub–page of EuiBasicTable
• [ ] Split out EuiTablePagination as a sub-page of EuiPagination
• [ ] Split out horizontal EuiSteps to its own subpage
• [ ] Split out different EuiBadge components to subpages
• [ ] Move markdown format + plugins to sub-pages of EuiMarkdownEditor
• [ ] EuiDataGrid - move each individual section to a sub-page of the main Data Grid page example
• [ ] Sidebar organization:
  • [ ] [Forms nav DX] The side nav order should match prod and not be alphabetical - this is ordered with highest use form controls coming first, as well as higher level other concepts (form row layouts, etc) coming before more alphabetized components
  • [ ] In memory table section should be below Tables section in sidebar