[Infra UI] Removed unused saved object attribute and unused source co…

…nfiguration code (#169430)

Resolves #168240

### Changes

- Removes `fields.message` from the `infrastructure-ui-source` saved
object who's value was being populated by
`xpack.infra.sources.default.fields.message` from config. See
https://www.elastic.co/guide/en/kibana/master/logs-ui-settings-kb.html
- Removes `getInternalSourceConfiguration` and
`defineInternalSourceConfiguration` functions introduced in
#36066 as I cannot see them being
used anywhere. Stops exposing `defineInternalSourceConfiguration` as
part of server plugin interface.
- Removes `getStaticDefaultSourceConfiguration` from InfraSources class
as we aren't using `sources` from kibana config in source configuration
anymore.
- Removes deprecations warning of removal in 8.0 for other fields
belonging to config xpack.infra.sources.* introduced in
#115103
- Removes `getAllSourceConfigurations` used only in removed deprecations
file
f427278#diff-081721894fc437938eb652beae0a0640ddeee532ec5e48af1f3093c8074f1eecL195
- Removed `getAllSavedSourceConfigurations` only used in
`getAllSourceConfigurations`

### How to test 
- `infrastructure-ui-source` saved object no longer has `fields`
attributes
- in kibana.yml set `xpack.infra.sources.default.fields.message:
['testmessage', '@testmessage']`
  - go to Infra -> Settings
  - Change the name and save the form
- view the `infrastructure-ui-source` saved object and no `fields`
attribute should exist (unless it previously existed in an already
existing `infrastructure-ui-source` saved object
- changes do not affect`fields.message` is used in logs_shared plugin
- i'm not sure how to easily test this and relying on someone with more
Logs knowledge to help out, but from what I can see logs accesses the
config directly (`xpack.infra.sources.default.fields.message`) and never
uses the saved object field being removed.

x-pack/plugins/infra/common/source_configuration/defaults.ts

@@ -16,9 +16,6 @@ export const defaultSourceConfiguration: InfraSourceConfiguration = {
     type: 'index_name',
     indexName: LOGS_INDEX_PATTERN,
   },
-  fields: {
-    message: ['message', '@message'],
-  },
   inventoryDefaultView: '0',
   metricsExplorerDefaultView: '0',
   logColumns: [

x-pack/plugins/infra/common/source_configuration/source_configuration.ts

@@ -17,29 +17,8 @@
 
 /* eslint-disable @typescript-eslint/no-empty-interface */
 
-import { omit } from 'lodash';
 import * as rt from 'io-ts';
 
-/**
- * Source configuration config file properties.
- * These are properties that can appear in the kibana.yml file.
- * This is a legacy method of providing properties, and will be deprecated in the future (v 8.0.0).
- */
-
-export const sourceConfigurationConfigFilePropertiesRT = rt.type({
-  sources: rt.type({
-    default: rt.partial({
-      fields: rt.partial({
-        message: rt.array(rt.string),
-      }),
-    }),
-  }),
-});
-
-export type SourceConfigurationConfigFileProperties = rt.TypeOf<
-  typeof sourceConfigurationConfigFilePropertiesRT
->;
-
 /**
  * Log columns
  */
@@ -104,47 +83,22 @@ export type LogIndexNameReference = rt.TypeOf<typeof logIndexNameReferenceRT>;
 export const logIndexReferenceRT = rt.union([logIndexPatternReferenceRT, logIndexNameReferenceRT]);
 export type LogIndexReference = rt.TypeOf<typeof logIndexReferenceRT>;
 
-/**
- * Fields
- */
-
-const SourceConfigurationFieldsRT = rt.type({
-  message: rt.array(rt.string),
-});
-
-/**
- * Properties that represent a full source configuration, which is the result of merging static values with
- * saved values.
- */
 export const SourceConfigurationRT = rt.type({
   name: rt.string,
   description: rt.string,
   metricAlias: rt.string,
   logIndices: logIndexReferenceRT,
   inventoryDefaultView: rt.string,
   metricsExplorerDefaultView: rt.string,
-  fields: SourceConfigurationFieldsRT,
   logColumns: rt.array(SourceConfigurationColumnRuntimeType),
   anomalyThreshold: rt.number,
 });
 
 /**
  * Stored source configuration as read from and written to saved objects
  */
-const SavedSourceConfigurationFieldsRuntimeType = rt.partial(
-  omit(SourceConfigurationFieldsRT.props, ['message'])
-);
 
-export type InfraSavedSourceConfigurationFields = rt.TypeOf<
-  typeof SavedSourceConfigurationFieldsRuntimeType
->;
-
-export const SavedSourceConfigurationRuntimeType = rt.intersection([
-  rt.partial(omit(SourceConfigurationRT.props, ['fields'])),
-  rt.partial({
-    fields: SavedSourceConfigurationFieldsRuntimeType,
-  }),
-]);
+export const SavedSourceConfigurationRuntimeType = rt.partial(SourceConfigurationRT.props);
 
 export interface InfraSavedSourceConfiguration
   extends rt.TypeOf<typeof SavedSourceConfigurationRuntimeType> {}
@@ -154,10 +108,8 @@ export interface InfraSavedSourceConfiguration
  * hardcoded defaults.
  */
 
-const StaticSourceConfigurationFieldsRuntimeType = rt.partial(SourceConfigurationFieldsRT.props);
 export const StaticSourceConfigurationRuntimeType = rt.partial({
   ...SourceConfigurationRT.props,
-  fields: StaticSourceConfigurationFieldsRuntimeType,
 });
 
 export interface InfraStaticSourceConfiguration
@@ -167,11 +119,8 @@ export interface InfraStaticSourceConfiguration
  * Full source configuration type after all cleanup has been done at the edges
  */
 
-export type InfraSourceConfigurationFields = rt.TypeOf<typeof SourceConfigurationFieldsRT>;
-
 export const SourceConfigurationRuntimeType = rt.type({
   ...SourceConfigurationRT.props,
-  fields: SourceConfigurationFieldsRT,
   logColumns: rt.array(SourceConfigurationColumnRuntimeType),
 });