[Markdown] Prepare Web/SVG docs for Markdowning

[wbamberg]

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

• remove id attributes except on headings: [Markdown] [Web/SVG] Remove SVG attribute IDs #9003, [Markdown] [Web/SVG] Fix SVG top example live samples #9002, [Markdown] [Web/SVG] Remove ID attributes from SVG docs #9037
• deal with hidden code blocks in live samples: [Markdown] [Web/SVG] Remove hidden DIVs from SVG docs #9074
• remove hidden elements that don't contain code blocks in a live sample (there are none!)
• remove summary and seoSummary class: [Markdown] [Web/SVG] Remove seoSummary and summary classes from SVG #8991
• remove inline styles: [Markdown] [Web/SVG] Remove inline styles from SVG docs #8972
• make note/warning consistently formatted: [Markdown] [Web/SVG] Fix notes and warnings #9040
• fix broken dl elements: [Markdown] [Web/SVG] Fix DL elements in the SVG docs #9038
• deal with sup and sub
• fix live samples that use IDs which are not simple derivations of heading text: [Markdown] [Web/SVG] Fix live sample ID arguments for SVG #9083
• remove random CSS classes: [Markdown] [Web/SVG] Miscellaneous SVG fixes for Markdown #9082
• remove unsupported elements: [Markdown] [Web/SVG] Miscellaneous SVG fixes for Markdown #9082
• ensure tables are converted appropriately: [Markdown] [Web/SVG] Make SVG docs consistently use properties tables #9118
• fix broken <strong><code> markup, and other inline markup issues (none found)

[wbamberg]

Finished, and converted with #9188.