[DOCS] Add identifier mapping tip to numeric and keyword datatype docs (#49933)

Users often mistakenly map numeric IDs to numeric datatypes. However,
this is often slow for the `term` and other term-level queries.

The "Tune for search speed" docs includes advice for mapping numeric
IDs to `keyword` fields. However, this tip is not included in the
`numeric` or `keyword` field datatype doc pages.

This rewords the tip in the "Tune for search speed" docs, relocates it
to the `numeric` field docs, and reuses it using tagged regions.

docs/reference/how-to/search-speed.asciidoc

@@ -159,13 +159,7 @@ GET index/_search
 [[map-ids-as-keyword]]
 === Consider mapping identifiers as `keyword`
 
-The fact that some data is numeric does not mean it should always be mapped as a
-<<number,numeric field>>. The way that Elasticsearch indexes numbers optimizes
-for `range` queries while `keyword` fields are better at `term` queries. Typically, 
-fields storing identifiers such as an `ISBN` or any number identifying a record 
-from another database are rarely used in `range` queries or aggregations. This is
-why they might benefit from being mapped as <<keyword,`keyword`>> rather than as 
-`integer` or `long`.
+include::../mapping/types/numeric.asciidoc[tag=map-ids-as-keyword]
 
 [float]
 === Avoid scripts

docs/reference/mapping/types/keyword.asciidoc

@@ -4,8 +4,8 @@
 <titleabbrev>Keyword</titleabbrev>
 ++++
 
-A field to index structured content such as email addresses, hostnames, status
-codes, zip codes or tags.
+A field to index structured content such as IDs, email addresses, hostnames,
+status codes, zip codes or tags.
 
 They are typically used for filtering (_Find me all blog posts where
 ++status++ is ++published++_), for sorting, and for aggregations. Keyword
@@ -30,6 +30,12 @@ PUT my_index
 }
 --------------------------------
 
+[TIP]
+.Mapping numeric identifiers
+====
+include::numeric.asciidoc[tag=map-ids-as-keyword]
+====
+
 [[keyword-params]]
 ==== Parameters for keyword fields
 

docs/reference/mapping/types/numeric.asciidoc

@@ -80,6 +80,31 @@ to help make a decision.
 |`half_float`|+2^-24^+ |+65504+ |+11+ / +3.31+
 |=======================================================================
 
+[TIP]
+.Mapping numeric identifiers
+====
+// tag::map-ids-as-keyword[]
+Not all numeric data should be mapped as a <<number,numeric>> field datatype.
+{es} optimizes numeric fields, such as `integer` or `long`, for
+<<query-dsl-range-query,`range`>> queries. However, <<keyword,`keyword`>> fields
+are better for <<query-dsl-term-query,`term`>> and other
+<<term-level-queries,term-level>> queries.
+
+Identifiers, such as an ISBN or a product ID, are rarely used in `range`
+queries. However, they are often retrieved using term-level queries.
+
+Consider mapping a numeric identifier as a `keyword` if:
+
+* You don't plan to search for the identifier data using 
+  <<query-dsl-range-query,`range`>> queries.
+* Fast retrieval is important. `term` query searches on `keyword` fields are
+  often faster than `term` searches on numeric fields.
+
+If you're unsure which to use, you can use a <<multi-fields,multi-field>> to map
+the data as both a `keyword` _and_ a numeric datatype.
+// end::map-ids-as-keyword[]
+====
+
 [[number-params]]
 ==== Parameters for numeric fields