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/windows/initial_access_script_executing_powershell.toml

@@ -1,7 +1,7 @@
 [metadata]
 creation_date = "2020/02/18"
 maturity = "production"
-updated_date = "2021/04/14"
+updated_date = "2022/03/31"
 
 [rule]
 author = ["Elastic"]
@@ -14,6 +14,10 @@ index = ["winlogbeat-*", "logs-endpoint.events.*", "logs-windows.*"]
 language = "eql"
 license = "Elastic License v2"
 name = "Windows Script Executing PowerShell"
+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 = 21
 rule_id = "f545ff26-3c94-4fd0-bd33-3c7f95a3a0fc"
 severity = "low"
@@ -31,17 +35,17 @@ process where event.type in ("start", "process_started") and
 framework = "MITRE ATT&CK"
 [[rule.threat.technique]]
 id = "T1566"
-reference = "https://attack.mitre.org/techniques/T1566/"
 name = "Phishing"
+reference = "https://attack.mitre.org/techniques/T1566/"
 [[rule.threat.technique.subtechnique]]
 id = "T1566.001"
-reference = "https://attack.mitre.org/techniques/T1566/001/"
 name = "Spearphishing Attachment"
+reference = "https://attack.mitre.org/techniques/T1566/001/"
 
 
 
 [rule.threat.tactic]
 id = "TA0001"
-reference = "https://attack.mitre.org/tactics/TA0001/"
 name = "Initial Access"
+reference = "https://attack.mitre.org/tactics/TA0001/"