Restructure usage-examples ES generated artifacts (elastic#1762)

* restructure generated dir structure

* update the example version to use 8.x

* cleanup usage-example es generated artifacts

* make dir structure in example command consistent

* drop -dev

* changelog entry

CHANGELOG.next.md

@@ -121,7 +121,7 @@ Thanks, you're awesome :-) -->
 * Removing use-cases directory #1405
 * Remove Go code generator. #1567
 * Remove template generation for ES6. #1680
-* Update folder structure for generated ES artifacts. #1700
+* Update folder structure for generated ES artifacts. #1700, #1762
 * Updated support for overridable composable settings template. #1737
 
 #### Improvements

usage-example/README.md

@@ -8,13 +8,13 @@ the `generated` directory contains the files generated by running the following
 command from the root of the ECS repository:
 
 ```bash
-python scripts/generator.py --ref v1.6.0 \
-  --subset            usage-example/fields/subset.yml \
-  --include           usage-example/fields/custom/ \
-  --out               usage-example/ \
-  --template-settings-legacy ../my-project/fields/template-settings-legacy.json \
-  --template-settings ../my-project/fields/template-settings.json \
-  --mapping-settings  usage-example/fields/mapping-settings.json
+python scripts/generator.py --ref v8.0.0 \
+  --subset                   usage-example/fields/subset.yml \
+  --include                  usage-example/fields/custom/ \
+  --out                      usage-example/ \
+  --template-settings-legacy usage-example/fields/template-settings-legacy.json \
+  --template-settings        usage-example/fields/template-settings.json \
+  --mapping-settings         usage-example/fields/mapping-settings.json
 ```
 
 Refer back to [USAGE.md](../USAGE.md) for the documentation on each of these flags.