Document default search technique change for Options List controls

The default search technique for newly created Options List controls changed
from Prefix to Contains in 9.4 (Kibana PR #250992).

- Add Searching options to the 9.4 tab (were missing) with Contains as default
- Mark Prefix as default in the 9.0-9.3 tab
- Use the actual UI label "Searching" (not "Search technique") in both tabs
- Fix setting order to match UI: Selections → Searching → Additional settings

Closes #4951

Author: florent-leborgne

explore-analyze/dashboards/add-controls.md

@@ -75,6 +75,13 @@ To add interactive Options list and Range slider controls, create the controls,
     * **Label**: Overwrite the default field name with a clearer and self-explanatory label.
     - **Selections**:
       Select multiple values to filter with the control, or only one.
+    - **Searching** (for Options list controls on *string* and *IP address* type fields):
+
+      * **Prefix** (default for *IP address* type fields): Show options that *start with* the entered value.
+      * **Contains** (default for *string* type fields): Show options that *contain* the entered value. This setting is only available for *string* type fields.
+      * **Exact**: Show options that are an *exact* match with the entered value.
+
+      The search is not case sensitive. For example, searching for `ios` would still retrieve `iOS` if that value exists.
     - **Additional settings**:
 
       - **Use global filters**: A panel-level setting that applies to each individual control. It is enabled by default.
@@ -90,17 +97,17 @@ To add interactive Options list and Range slider controls, create the controls,
     - **Selections**:
       Select multiple values to filter with the control, or only one.
 
-    - **Additional settings**:
-
-      - **Ignore timeout for results**: Delays the display of the list of values until it is fully loaded. This option is useful for large data sets, to avoid missing some available options in case they take longer to load and appear when using the control.
-
-      For Options list controls on *string* and *IP address* type fields, you can define how the control’s embedded search should behave:
+    - **Searching** (for Options list controls on *string* and *IP address* type fields):
 
-      * **Prefix**: Show options that *start with* the entered value.
-      * **Contains**: Show options that *contain* the entered value. This setting option is only available for *string* type fields. Results can take longer to show with this option.
+      * **Prefix** (default): Show options that *start with* the entered value.
+      * **Contains**: Show options that *contain* the entered value. This setting is only available for *string* type fields.
       * **Exact**: Show options that are an *exact* match with the entered value.
 
       The search is not case sensitive. For example, searching for `ios` would still retrieve `iOS` if that value exists.
+
+    - **Additional settings**:
+
+      - **Ignore timeout for results**: Delays the display of the list of values until it is fully loaded. This option is useful for large data sets, to avoid missing some available options in case they take longer to load and appear when using the control.
     :::
 
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