docs: add __state_clear intrinsic documentation to Sway Book, close #…

[ritik4ever]

…4306
This PR adds documentation for the __state_clear intrinsic function to the compiler intrinsics reference in the Sway Book. The function was previously not documented as noted in issue #4306.

Changes Made

• Added a detailed description of the __state_clear intrinsic function
• Included syntax, return value, example usage, and usage notes
• Formatted consistently with other intrinsic function documentation

Related Issue

Closes #4306

Additional Notes

I made sure to include important usage warnings since this is a function that clears all contract storage and should be used with caution.

[fuel-cla-bot]

Thanks for the contribution! Before we can merge this, we need @ritik4ever to sign the Fuel Labs Contributor License Agreement.

[IGI-111]

The markdown linter is still complaining:

docs/book/src/reference/compiler_intrinsics.md:1 MD022/blanks-around-headings/blanks-around-headers Headings should be surrounded by blank lines [Expected: 1; Actual: 0; Below] [Context: "# Compiler Intrinsics"]
docs/book/src/reference/compiler_intrinsics.md:2 MD001/heading-increment/header-increment Heading levels should only increment by one level at a time [Expected: h2; Actual: h3]
docs/book/src/reference/compiler_intrinsics.md:2 MD022/blanks-around-headings/blanks-around-headers Headings should be surrounded by blank lines [Expected: 1; Actual: 0; Above] [Context: "### `__state_clear`"]
docs/book/src/reference/compiler_intrinsics.md:4:20 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]