fixes [`DatePicker` dialog contents are hidden when using smaller text size](https://github.com/flutter/flutter/issues/139120)

### Description
- Fixed `DatePicker` dialog contents are hidden when using smaller text size.
- Add golden tests

### Golden Test (Before)

| `TextScale - 0.88` | `TextScale - 1.0` | `TextScale - 2.0` | 
| --------------- |  --------------- |  --------------- | 
|   <img src="https://github.com/flutter/flutter/assets/48603081/9f301c5d-3acd-4a9f-8fb7-aa7b2e9553a2"> |  <img src="https://github.com/flutter/flutter/assets/48603081/0496cf1a-5086-4cb1-ad3f-256f34346920"> | <img src="https://github.com/flutter/flutter/assets/48603081/2d1e1892-435a-4938-a7fc-2ffa4684828b"> | 

### Golden Test (After)

| `TextScale - 0.88` | `TextScale - 1.0` | `TextScale - 2.0` | 
| --------------- |  --------------- |  --------------- | 
|   <img src="https://github.com/flutter/flutter/assets/48603081/8fb922b7-0f2c-4f08-a091-b359a01e3600"> |  <img src="https://github.com/flutter/flutter/assets/48603081/59933cbf-49ef-46fb-98b5-217db2cc0ee7"> | <img src="https://github.com/flutter/flutter/assets/48603081/fd2501cb-511c-4b57-a4eb-f583af60aed7"> |