* #1029 - 8 vector_store_similarity_search and SpannerVectorStoreSettings
Added vector_store_similarity_search to SpannerToolset. SpannerVectorStoreSettings is introduced to support this feature.
* Update spanner.md
* Update spanner.md
Applied feedback. Additionally, reviewed the phrasing in the intro for clarity and concision and did some minor formatting edits.
* Fix wrapping, missing import, trailing whitespace, formatting fixes
* Restructure Spanner page: add intro, section headings, reorder vector search
* Add experimental tags/notes to corresponding integration pages
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Co-authored-by: Kristopher Overholt <koverholt@google.com>
Zyan