add fetch billing products from tables instead of env variables (#9601)

Solves https://github.com/twentyhq/private-issues/issues/237

**TLDR:**

- Fetches billing products and prices from the tables BilllingProducts
and BillingPrices instead of fetching the product from the environment
variables and the prices from the stripe API.
- Adds new feature flag for this feature
- Fixes calls used to fetch stripe products and prices for the command
Billing Sync Plans Data.


**In order to test:**

1. Have the environment variable IS_BILLING_ENABLED set to true and add
the other required environment variables for Billing to work
2. Do a database reset (to ensure that the new feature flag is properly
added and that the billing tables are created)
3. Run the command: `npx nx run twenty-server:command
billing:sync-plans-data` (if you don't do that the products and prices
will not be present in the database)
4. Run the server , the frontend, the worker, and the stripe listen
command (`stripe listen --forward-to
http://localhost:3000/billing/webhooks`)
5. Buy a subscription for the Acme workspace and play with the project

**Doing**

I think there is some room of progress for the function
formatProductPrices, I used a similar version that was done before, I'll
look into that.

packages/twenty-server/src/engine/core-modules/client-config/client-config.entity.ts

@@ -1,6 +1,6 @@
 import { Field, ObjectType, registerEnumType } from '@nestjs/graphql';
 
-import { TrialPeriodDTO } from 'src/engine/core-modules/billing/dto/trial-period.dto';
+import { BillingTrialPeriodDTO } from 'src/engine/core-modules/billing/dtos/billing-trial-period.dto';
 import { CaptchaDriverType } from 'src/engine/core-modules/captcha/interfaces';
 import { FeatureFlagKey } from 'src/engine/core-modules/feature-flag/enums/feature-flag-key.enum';
 import { AuthProviders } from 'src/engine/core-modules/workspace/dtos/public-workspace-data-output';
@@ -17,8 +17,8 @@ class Billing {
   @Field(() => String, { nullable: true })
   billingUrl?: string;
 
-  @Field(() => [TrialPeriodDTO])
-  trialPeriods: TrialPeriodDTO[];
+  @Field(() => [BillingTrialPeriodDTO])
+  trialPeriods: BillingTrialPeriodDTO[];
 }
 
 @ObjectType()