ElasticsearchIndexerController Should Load Relations Using relationLoadStrategy "query"

[floze]

By simply adding the relationLoadStrategy typeorm find flag and setting it to "query" on the following two occasions, the indexing speed improved by ~500% in our setup:

vendure/packages/elasticsearch-plugin/src/indexing/indexer.controller.ts

Line 502 in 758e92d

.find({

vendure/packages/elasticsearch-plugin/src/indexing/indexer.controller.ts

Line 516 in 758e92d

updatedProductVariants = await this.connection.rawConnection.getRepository(ProductVariant).find({