Clean up optimization docs & add syntactic join ordering section

[colebow]

Description

Improvements to optimization docs (formatting & grammar), then adding a new section on how to best optimize for syntactic join ordering.

Is this change a fix, improvement, new feature, refactoring, or other?

Improvement

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)

Docs

Documentation

( ) No documentation is needed. (x) Sufficient documentation is included in this PR. ( ) Documentation PR is available with #prnumber. ( ) Documentation issue #issuenumber is filed, and can be handled later.

Release notes

(x) No release notes entries required. ( ) Release notes entries required with the following suggested text: