cli: add cluster_settings_history.txt to debug zip

Adds a new file exported to debug zip called
"cluster_settings_history.txt" which provides a history
of cluster setting changes, as they exist in the system
event log table. This means history will only exist as
long as the events haven't been removed from the table.

Sensitive cluster settings will always be redacted in
this file, and non reportable cluster settings will be
redacted for redacted debug zips.

Epic: CRDB-52093
Resolves: CRDB-50883
Release note (cli change): Adds a new file to debug zip
that provides a history of cluster setting changes.
Sensitive cluster settings will always be redacted in
this file, and non reportable cluster settings will be
redacted for redacted debug zips.

Author: kyle-a-wong

pkg/cli/testdata/zip/file-filters/testzip_file_filters

@@ -1,6 +1,7 @@
 #include all filters. We are excluding cpu.pprof file to avoid flakiness in tests.
 --include-files=* --exclude-files=cpu.pprof
 ----
+debug/cluster_settings_history.txt
 debug/crdb_internal.cluster_contention_events.txt
 debug/crdb_internal.cluster_database_privileges.txt
 debug/crdb_internal.cluster_distsql_flows.txt
@@ -144,6 +145,7 @@ debug/tenant_ranges.err.txt
 #include only txt files
 --include-files=*.txt
 ----
+debug/cluster_settings_history.txt
 debug/crdb_internal.cluster_contention_events.txt
 debug/crdb_internal.cluster_database_privileges.txt
 debug/crdb_internal.cluster_distsql_flows.txt
@@ -294,6 +296,7 @@ debug/tenant_ranges.err.txt
 #exclude only log files. We are excluding cpu.pprof file to avoid flakiness in tests.
 --exclude-files=*.log,cpu.pprof
 ----
+debug/cluster_settings_history.txt
 debug/crdb_internal.cluster_contention_events.txt
 debug/crdb_internal.cluster_database_privileges.txt
 debug/crdb_internal.cluster_distsql_flows.txt
@@ -438,6 +441,7 @@ debug/tenant_ranges.err.txt
 #exclude only json files. We are excluding cpu.pprof file to avoid flakiness in tests.
 --exclude-files=*.json,cpu.pprof
 ----
+debug/cluster_settings_history.txt
 debug/crdb_internal.cluster_contention_events.txt
 debug/crdb_internal.cluster_database_privileges.txt
 debug/crdb_internal.cluster_distsql_flows.txt
@@ -550,6 +554,7 @@ debug/tenant_ranges.err.txt
 #include only txt files with system table file exclustion
 --include-files=*.txt --exclude-files=system.*.txt
 ----
+debug/cluster_settings_history.txt
 debug/crdb_internal.cluster_contention_events.txt
 debug/crdb_internal.cluster_database_privileges.txt
 debug/crdb_internal.cluster_distsql_flows.txt

pkg/cli/zip_table_registry.go

@@ -674,6 +674,61 @@ FROM crdb_internal.transaction_contention_events
 			"full_config_sql",
 		},
 	},
+	// cluster_settings_history Provides a history of cluster settings changes
+	// via the system.eventlog table. If the value is reset via `RESET
+	// CLUSTER SETTING <x>`, the value is shown as 'DEFAULT'. This can be used
+	// to distinguish between when a user explicitly sets the value to the
+	// default value via `SET CLUSTER SETTING <x> = <y>`. For cluster settings
+	// set in v25.4+, the `default_value` column will show the default value
+	// for the setting at the time of the change, which may differ from the
+	// current default value.
+	// The `value` column will always be redacted if the setting is sensitive.
+	// If a redacted debug zip is requested, non-reportable settings will
+	// also be redacted.
+	"cluster_settings_history": {
+		customQueryUnredacted: `
+WITH setting_events AS (
+	SELECT
+		timestamp,
+		info::jsonb AS info_json
+	FROM system.eventlog
+	WHERE "eventType" = 'set_cluster_setting'
+)
+SELECT
+	info_json ->> 'SettingName' as setting_name,
+	CASE
+      WHEN cs.sensitive AND info_json ->> 'Value' <> 'DEFAULT' THEN '<redacted>'
+      ELSE info_json ->> 'Value'
+	END value,
+	info_json ->> 'DefaultValue' as default_value,
+	cs.default_value as current_default_value,
+	info_json ->> 'ApplicationName' as application_name,
+	se.timestamp
+FROM setting_events se
+JOIN crdb_internal.cluster_settings cs on cs.variable = se.info_json ->> 'SettingName'
+ORDER BY setting_name, timestamp`,
+		customQueryRedacted: `
+WITH setting_events AS (
+	SELECT
+		timestamp,
+		info::jsonb AS info_json
+	FROM system.eventlog
+	WHERE "eventType" = 'set_cluster_setting'
+)
+SELECT
+	info_json ->> 'SettingName' as setting_name,
+	CASE
+      WHEN (cs.sensitive OR NOT cs.reportable) AND info_json ->> 'Value' <> 'DEFAULT' THEN '<redacted>'
+      ELSE info_json ->> 'Value'
+ 	END value,
+	info_json ->> 'DefaultValue' as default_value,
+	cs.default_value as current_default_value,
+	info_json ->> 'ApplicationName' as application_name,
+	se.timestamp
+FROM setting_events se
+JOIN crdb_internal.cluster_settings cs on cs.variable = se.info_json ->> 'SettingName'
+ORDER BY setting_name, timestamp`,
+	},
 }
 
 var zipInternalTablesPerNode = DebugZipTableRegistry{

pkg/cli/zip_test.go

@@ -135,6 +135,7 @@ ORDER BY name ASC`)
 		tables = append(tables, table)
 	}
 	tables = append(tables, "crdb_internal.probe_ranges_1s_read_limit_100")
+	tables = append(tables, "cluster_settings_history")
 	sort.Strings(tables)
 
 	var exp []string