Add back missing process command-line fields (elastic#8258)

The fields `cmdline` and `client_cmdline`, that were recently added to
packetbeat, were missing as the feature was merged in parallel to a
refactor of the fields generation.

CHANGELOG.asciidoc

@@ -79,6 +79,7 @@ https://github.com/elastic/beats/compare/v6.4.0...master[Check the HEAD diff]
 
 - Fixed a seccomp related error where the `fcntl64` syscall was not permitted
   on 32-bit Linux and the sniffer failed to start. {issue}7839[7839]
+- Added missing `cmdline` and `client_cmdline` fields to index template. {pull}8258[8258]
 
 *Winlogbeat*
 

packetbeat/_meta/fields.common.yml

@@ -79,10 +79,18 @@
       description: >
         The name of the process that served the transaction.
 
+    - name: cmdline
+      description: >
+        The command-line of the process that served the transaction.
+
     - name: client_proc
       description: >
         The name of the process that initiated the transaction.
 
+    - name: client_cmdline
+      description: >
+        The command-line of the process that initiated the transaction.
+
     - name: release
       description: >
         The software release of the service serving the transaction.

packetbeat/docs/fields.asciidoc

@@ -1492,6 +1492,14 @@ The layer 4 port of the process that served the transaction.
 The name of the process that served the transaction.
 
 
+--
+
+*`cmdline`*::
++
+--
+The command-line of the process that served the transaction.
+
+
 --
 
 *`client_proc`*::
@@ -1500,6 +1508,14 @@ The name of the process that served the transaction.
 The name of the process that initiated the transaction.
 
 
+--
+
+*`client_cmdline`*::
++
+--
+The command-line of the process that initiated the transaction.
+
+
 --
 
 *`release`*::