Azure Form Recognizer client library samples for TypeScript

[FormRecognizer] Rename for cross-language API consistency (#8808)

* [FormRecognizer] Rename for cross-language API consistency

- `beginRecognizeForms` => `beginRecognizeCustomForms`

* FormElement => FormContent

* blobContainerUrl => trainingFilesUrl

* parameter name `documentUrl` => `formFileUrl` or `receiptFileUrl`

* useLabels => useTrainingLabels, getModel => getCustomModel

* listModels => listCustomModels

* ModelInfo => CustomFormModelInfo

* limit => customModelLimit, count => customModelCount

* fieldLabel => labelText

* ErrorInformation => FormRecognizerError

export `Model` from model.ts instead of from generated code.

* CustomFormSubModelField => CustomFormField

* ModelStatus => CustomFormModelStatus

TrainStatus => TrainingStatus