[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
• In memory table section should be below Tables section in sidebar
• [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
• Remove Templates category per team discussion on Slack:
  • Move EuiSuperDatePicker to Forms
  • Move EuiPageTemplate to Layout
  • Move EuiSelectableTemplateSitewide to Navigation

[cee-chen]

Unassigning myself from this issue. Someone will need to take over #8183 and #8184 and get them merged.

Once they're in, the only remaining task item is:

Split out EuiTablePagination as a sub-page of EuiPagination

Although IMO I'd be fine closing out this issue without it, as the pagination page feels mostly fine/not too crowded as-is currently. Alternatively, it might be interesting to move EuiTablePagination to a Tables subpage instead? 🤔 Up to you all on that one.

EDIT: Oh, I also added an item we brought up in Slack recently, which is removing the Templates category altogether. I do think that change would be a nice DX improvement.