[Markdown] Prepare Web/HTML docs for Markdowning

[wbamberg]

This is a tracking bug for the work we have to do to prepare the Web/HTML documentation for Markdown conversion.

• remove id attributes except on headings:
  • [Markdown] [Web/HTML] Remove DIV IDs from HTML docs, part 1 #9009,
  • [Markdown] [Web/HTML] Remove DIV IDs from HTML elements, part 2 #9031,
  • [Markdown] [Web/HTML] Remove page macro from input element pages #9033
  • [Markdown] [Web/HTML] Remove ID attributes from HTML input page #9124
  • [Markdown] [Web/HTML] Remove ID attribute from HTML input types #9125
  • [Markdown] [Web/HTML] Remove ID attributes from HTML docs: everything except input #9128
• deal with hidden code blocks in live samples: [Markdown] [Web/HTML] Remove hidden divs #9158
• remove hidden elements that don't contain code blocks in a live sample: [Markdown] Remove hidden no-code elements from HTML docs #8962
• remove summary and seoSummary class: [Markdown] Remove seoSummary and summary classes from HTML docs #8964
• remove inline styles: [Markdown] Remove style attribute from HTML docs #8966
• make note/warning consistently formatted:
  • [Markdown] [Web/HTML] Fix notes in HTML pages that have misplaced colons #9130
  • [Markdown] [Web/HTML] Fix HTML notes that aren't in a P #9134
  • [Markdown] [Web/HTML] Add "Note:" prefix #9151
  • [Markdown] [Web/HTML] Fix heading-style notes #9152
  • [Markdown] [Web/HTML] Fix up remaining notes #9154
  • [Markdown] [Web/HTML] Fix remaining notes and warnings in HTML docs #9214
• fix broken dl elements: [Markdown] Fix unconvertible <dl> elements in HTML #8963
• deal with sup and sub
• fix live samples that use IDs which are not simple derivations of heading text: [Markdown] [Web/HTML] Remove ID attributes from HTML docs: everything except input #9128
• remove random CSS classes: [Markdown] [Web/HTML] Miscellaneous markup fixes #9157, [Markdown] [Web/HTML] More miscellaneous fixes #9215
• remove unsupported elements: [Markdown] [Web/HTML] Miscellaneous markup fixes #9157, [Markdown] [Web/HTML] More miscellaneous fixes #9215
• ensure tables are converted appropriately: [Markdown] [Web/HTML] Suppress conversion of wide tables #9216
• fix broken <strong><code> markup, and other inline markup issues (none found)

[wbamberg]

Prep done, and conversion done in #9303 .