[SQL][DOCS] Improve table caching section

Author: Michael Armbrust <michael@databricks.com>

Closes #2434 from marmbrus/patch-1 and squashes the following commits:

67215be [Michael Armbrust] [SQL][DOCS] Improve table caching section

(cherry picked from commit cbf983bb4a550ff26756ed7308fb03db42cffcff)
Signed-off-by: Michael Armbrust <michael@databricks.com>
Docs: move HA subsections to a deeper indentation level

Makes the table of contents read better

Author: Andrew Ash <andrew@andrewash.com>

Closes #2402 from ash211/docs/better-indentation and squashes the following commits:

ea0e130 [Andrew Ash] Move HA subsections to a deeper indentation level

(cherry picked from commit b3830b28f8a70224d87c89d8491c514c4c191d23)
Signed-off-by: Andrew Or <andrewor14@gmail.com>