Contact Shadows (#22382)

# Objective

- Implement contact shadows to add fine shadow detail where shadow
cascades cannot.

## Solution

- Extend our existing pbr implementation using our existing raymarching
functions.

---

## Showcase

<img width="1824" height="1180" alt="image"
src="https://github.com/user-attachments/assets/e93b79c5-c596-4a9e-b94d-20bdde1d863b"
/>

<img width="1824" height="1180" alt="image"
src="https://github.com/user-attachments/assets/0fd7dffa-60b8-4b92-8fad-7f993d4d89dd"
/>


https://github.com/user-attachments/assets/e74b190d-9ae3-4aaf-97f0-b520930a0667


https://github.com/user-attachments/assets/e80ccb26-bbaa-4d25-a823-8ea12354c5b9


https://github.com/user-attachments/assets/b04f4b00-92bd-4a2f-b7dd-5157d8fbe0ab

<img width="1073" height="685" alt="image"
src="https://github.com/user-attachments/assets/b7629908-dd32-48db-8ee7-a4d2dd8f66c2"
/>

<img width="1073" height="685" alt="image"
src="https://github.com/user-attachments/assets/3de0258e-9191-4180-ac57-41b32e1205bd"
/>

<img width="1073" height="685" alt="image"
src="https://github.com/user-attachments/assets/951477f9-e9a9-426f-ae8d-18ae50cc7b85"
/>

<img width="1073" height="685" alt="image"
src="https://github.com/user-attachments/assets/2291453c-da57-4fcc-a6b0-f60f6eac6cbb"
/>

<img width="1073" height="685" alt="image"
src="https://github.com/user-attachments/assets/5820cdff-ea54-4294-b520-2a8d8dc24996"
/>

<img width="1073" height="685" alt="image"
src="https://github.com/user-attachments/assets/3ea16481-7689-4e99-87e2-1589f1532e4c"
/>

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Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: charlotte 🌸 <charlotte.c.mcelwain@gmail.com>