Install all packages in mage (#17388)

##  What does this PR do?

This PR fixes the install command of `mage`. With the adoption of go modules adding `/...` has become necessary in order to install the pacakge.

## Why is it important?

This issue prevents beats from installing `mage` if it is not present. One of the symptoms of this problem is the failure to generate new Beats if `mage` is not available.

dev-tools/make/mage.mk

@@ -7,7 +7,7 @@ export MAGE_IMPORT_PATH
 mage:
 ifndef MAGE_PRESENT
 	@echo Installing mage $(MAGE_VERSION) from vendor dir.
-	go install -mod=vendor -ldflags="-X $(MAGE_IMPORT_PATH)/mage.gitTag=$(MAGE_VERSION)" ${MAGE_IMPORT_PATH}
+	go install -mod=vendor -ldflags="-X $(MAGE_IMPORT_PATH)/mage.gitTag=$(MAGE_VERSION)" ${MAGE_IMPORT_PATH}/...
 	@-mage -clean
 endif
 	@true