Reformat search API docs

[jrodewig]

Updates the search API documentation to match the Elastic API reference template.

Relates to elastic/docs#937 and #45195

• Search ([DOCS] Reformats search API #45786)
• URI Search ([DOCS] Reformats URI search request #45844)
• Request Body Search ([DOCS] Reformats request body search API #46254)
• Search Template ([DOCS] Reformats search template and multi search template APIs #46236)
• Multi Search Template ([DOCS] Reformats search template and multi search template APIs #46236)
• Search Shards API ([DOCS] Reformats search shards API #46240)
• Suggesters ([DOCS] Reformat suggesters page #47010)
• Multi Search API ([DOCS] Reformats multi search API #46256)
• Count API ([DOCS] Reformats count API #46377)
• Validate API ([DOCS] Reformats validate API #46389)
• Explain API ([DOCS] Reformats explain API #46857)
• Profile API ([DOCS] Reformats Profile API #47168)
• Field Capabilities API ([DOCS] Reformats Field capabilities API #46866)
• Ranking Evaluation API ([DOCS] Reformats ranking evaluation API #46974)

We are only backporting these changes to 7.x and 7.3.

If you begin working on an API, please indicate it as a WIP here to prevent duplicating efforts.

Example

Before: https://www.elastic.co/guide/en/elasticsearch/reference/7.0/cat-indices.html
After: https://www.elastic.co/guide/en/elasticsearch/reference/master/cat-indices.html

Please feel free to reach out to @jrodewig or @lcawl if you run into issues or questions.

[elasticmachine]

Pinging @elastic/es-search

[elasticmachine]

Pinging @elastic/es-docs