Expand timestamp override tests (#1907)

* Expand timestamp_override tests
* removed timestamp_override from eql sequence rules
* add config entry for eql rules with beats index and t_o
* add timestamp_override to missing fields

Removed changes from:
- rules/cross-platform/impact_hosts_file_modified.toml
- rules/windows/credential_access_lsass_memdump_file_created.toml
- rules/windows/defense_evasion_adding_the_hidden_file_attribute_with_via_attribexe.toml
- rules/windows/defense_evasion_execution_lolbas_wuauclt.toml
- rules/windows/defense_evasion_suspicious_certutil_commands.toml
- rules/windows/execution_command_shell_started_by_svchost.toml

(selectively cherry picked from commit 6bdfddac8e)

rules/cross-platform/execution_python_script_in_cmdline.toml

@@ -1,7 +1,7 @@
 [metadata]
 creation_date = "2021/01/13"
 maturity = "development"
-updated_date = "2021/03/03"
+updated_date = "2022/03/31"
 
 [rule]
 author = ["Elastic"]
@@ -15,6 +15,10 @@ index = ["auditbeat-*", "logs-endpoint.events.*"]
 language = "eql"
 license = "Elastic License v2"
 name = "Python Script Execution via Command Line"
+note = """## Config
+
+If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.
+"""
 risk_score = 47
 rule_id = "ee9f08dc-cf80-4124-94ae-08c405f059ae"
 severity = "medium"