[DOCS] Add searchable snapshots topic. (#63040)

[debadair]

• [DOCS] Add searchable snapshots topic.

• [DOCS] Add definitions & remove fully-remote storage.

• [DOCS] Fixed duplicate anchor.

• Expand conceptual docs for searchable snapshots

• Rewordings

• Glossary tidy-up

• Beta

• Reword

• More performance idea to a TIP

• use -> manage

• red -> not green

• Missing space?

• Update docs/reference/glossary.asciidoc

• Fix beta label

• Use more attributes, fix link titles

• Apply suggestions from code review

Co-authored-by: debadair [email protected]

• Reformat

• Minor rewordings

• More minor rewordings

• Address Henning's comments

Co-authored-by: David Turner [email protected]
Co-authored-by: James Rodewig [email protected]

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[elasticmachine]

Pinging @elastic/es-docs (>docs)

[elasticmachine]

Pinging @elastic/es-docs (:Docs)