[Heartbeat] Move import to cmd for agentbeat (#39818) (#39819)

* [Heartbeat] Move import to cmd for agentbeat

Fix browser plugin import to be bundled inside agentbeat, which is now being skipped and it prevents browser monitors from working.

(cherry picked from commit 727777e)

Co-authored-by: Emilio Alvarez Piñeiro <95703246+emilioalvap@users.noreply.github.com>

CHANGELOG.next.asciidoc

@@ -81,6 +81,12 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 
 *Heartbeat*
 
+- Fix panics when parsing dereferencing invalid parsed url. {pull}34702[34702]
+- Fix setuid root when running under cgroups v2. {pull}37794[37794]
+- Adjust State loader to only retry when response code status is 5xx {pull}37981[37981]
+- Reset prctl dumpable flag after cap drop. {pull}38269[38269]
+- Redact synthexec cmd output. {pull}39535[39535]
+- Fix import of browser plugin for agentbeat. {pull}39818[39818]
 
 *Heartbeat*
 

x-pack/heartbeat/import.go → x-pack/heartbeat/cmd/import.go

@@ -4,8 +4,10 @@
 
 //go:build linux || darwin
 
-package main
+package cmd
 
+// Agentbeat imports cmd directly and skips main, import all required plugins
+// here to have them bundled together
 import (
 	_ "github.com/elastic/beats/v7/x-pack/heartbeat/monitors/browser"
 )