## Summary

The purpose of this PR is to make the spaces plugin an optional
dependency so that it can be disabled in future offerings.

In order to achieve this we are reintroducing the following config
option to disable spaces:

```yaml
xpack.spaces.enabled: false
```

This config option is only available in development mode while we
coordinate updating the rest of our plugins.

## Scope

In order to keep the scope manageable, only the following plugins have
been updated as part of this PR:

- `x-pack/plugins/alerting`
- `x-pack/plugins/security`
- `x-pack/plugins/spaces`

The following plugins will need to be updated separately, by working
with the corresponding teams:

- `x-pack/plugins/cases`
- `x-pack/plugins/enterprise_search`
- `x-pack/plugins/fleet`
- `x-pack/plugins/infra`
- `x-pack/plugins/lens`
- `x-pack/plugins/ml`
- `x-pack/plugins/observability`
- `x-pack/plugins/osquery`
- `x-pack/plugins/synthetics`

## Screenshots

### Kibana chrome without spaces selector

<img width="1073" alt="212935199-dd3bb035-b2f5-4fb6-96e9-5d2093c7992c"
src="https://user-images.githubusercontent.com/190132/213432556-18e1c159-1fb1-4808-ad12-47814de575ed.png">

### Simplified role management screen

<img width="1136" alt="Screenshot 2023-01-19 at 11 21 03"
src="https://user-images.githubusercontent.com/190132/213432595-0ae33abb-85e7-4044-82a2-6cc44304af0e.png">

closing #155329


<details>
  <summary>files using space id</summary>
  
```
apm • server/routes/alerts/rule_types/anomaly/register_anomaly_rule_type.ts:
   19  import { createLifecycleRuleTypeFactory } from '@kbn/rule-registry-plugin/server';
   20: import { addSpaceIdToPath } from '@kbn/spaces-plugin/common';
   21  import { compact } from 'lodash';

   89        isExportable: true,
   90:       executor: async ({ params, services, spaceId }) => {
   91          if (!ml) {

  278  
  279:           const viewInAppUrl = addSpaceIdToPath(
  280              basePath.publicBaseUrl,
  281:             spaceId,
  282              relativeViewInAppUrl

apm • server/routes/alerts/rule_types/error_count/register_error_count_rule_type.ts:
   19  import { termQuery } from '@kbn/observability-plugin/server';
   20: import { addSpaceIdToPath } from '@kbn/spaces-plugin/common';
   21  import { firstValueFrom } from 'rxjs';

   88        isExportable: true,
   89:       executor: async ({ params: ruleParams, services, spaceId }) => {
   90:         console.log('spaceId executor====', spaceId);
   91          const predefinedGroupby = [SERVICE_NAME, SERVICE_ENVIRONMENT];

  189  
  190:             const viewInAppUrl = addSpaceIdToPath(
  191                basePath.publicBaseUrl,
  192:               spaceId,
  193                relativeViewInAppUrl

apm • server/routes/alerts/rule_types/transaction_duration/register_transaction_duration_rule_type.ts:
   22  import { createLifecycleRuleTypeFactory } from '@kbn/rule-registry-plugin/server';
   23: import { addSpaceIdToPath } from '@kbn/spaces-plugin/common';
   24  import { firstValueFrom } from 'rxjs';

  104      isExportable: true,
  105:     executor: async ({ params: ruleParams, services, spaceId }) => {
  106        const predefinedGroupby = [

  257            basePath,
  258:           spaceId,
  259            alertUuid

  261  
  262:         const viewInAppUrl = addSpaceIdToPath(
  263            basePath.publicBaseUrl,
  264:           spaceId,
  265            getAlertUrlTransaction(

apm • server/routes/alerts/rule_types/transaction_error_rate/register_transaction_error_rate_rule_type.ts:
   20  import { createLifecycleRuleTypeFactory } from '@kbn/rule-registry-plugin/server';
   21: import { addSpaceIdToPath } from '@kbn/spaces-plugin/common';
   22  import { firstValueFrom } from 'rxjs';

   98        isExportable: true,
   99:       executor: async ({ services, spaceId, params: ruleParams }) => {
  100:         console.log('error rate executor space', spaceId);
  101          const predefinedGroupby = [

  251  
  252:           const viewInAppUrl = addSpaceIdToPath(
  253              basePath.publicBaseUrl,
  254:             spaceId,
  255              relativeViewInAppUrl

apm • server/routes/service_groups/get_service_group_alerts.ts:
  24    logger,
  25:   spaceId,
  26  }: {

  30    logger: Logger;
  31:   spaceId?: string;
  32  }) {
  33:   if (!spaceId || serviceGroups.length === 0) {
  34      return {};

apm • server/routes/service_groups/route.ts:
  189          logger,
  190:         spaceId: activeSpace?.id ?? DEFAULT_SPACE_ID,
  191        }),

apm • server/saved_objects/migrations/migrate_legacy_apm_indices_to_space_aware.ts:
  79          // Skip default space since it was already updated
  80:         .filter(({ id: spaceId }) => spaceId !== 'default')
  81:         .map(({ id: spaceId }) => ({
  82            id: APM_INDEX_SETTINGS_SAVED_OBJECT_ID,
  83            type: APM_INDEX_SETTINGS_SAVED_OBJECT_TYPE,
  84:           initialNamespaces: [spaceId],
  85            attributes: savedObjectAttributes,

apm • public/components/app/settings/apm_indices/index.tsx:
  105    const { data: space } = useFetcher(() => {
  106:     return services.spaces?.getActiveSpace();
  107    }, [services.spaces]);

apm • server/routes/service_groups/route.ts:
  174          getApmEventClient(resources),
  175:         await spacesPluginStart?.spacesService.getActiveSpace(request),
  176        ]);


  ```
</details>


### Notes 
it's a bit challenging to ensure the other plugins return the default space or have the plugin as optional. How do we want to handle these cases, if there are any? 

for example, alert returns default space when the plugin is disabled. 


Relate link PR
#149044