bump six labors

[jakubmisek]

update SixLabors dependencies to latest version

ref #1144

[Copilot]

Pull Request Overview

This PR updates the SixLabors dependencies to their latest versions and adapts the image‐processing code to breaking API changes in ImageSharp, ImageSharp.Drawing, and SixLabors.Fonts.

• Bumped SixLabors.ImageSharp, SixLabors.ImageSharp.Drawing, and SixLabors.Fonts package versions.
• Migrated from older drawing/renderer options APIs (e.g., ShapeGraphicsOptions, RendererOptions) to the new DrawingOptions, TextOptions, etc.
• Replaced deprecated constructors and methods (e.g., Image.Load(..., out var format), ConfigurationModule) with the updated overloads and configuration types.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Peachpie.Runtime/Variables.cs	Annotated string return types as nullable and added nullability annotation for out parameters.
src/Peachpie.Library.Graphics/PhpGdImageResource.cs	Updated IBrush to Brush and adapted constructors to new config interfaces.
src/Peachpie.Library.Graphics/PhpGd2.cs	Switched to new ImageSharp.Drawing APIs, updated XML docs, and replaced deprecated SixLabors calls.
src/Peachpie.Library.Graphics/Peachpie.Library.Graphics.csproj	Bumped SixLabors package versions to 3.x/2.x series.
src/Peachpie.Library.Graphics/FloodFillProcessor{TPixel}.cs	Wrapped pixel operations in ProcessPixelRows and switched to GetRowSpan.
src/Peachpie.Library.Graphics/Exif.cs	Refactored Exif handling to use updated SixLabors metadata APIs and pattern matching.

[Copilot]

[nitpick] The summary line would read more clearly with punctuation between clauses. Consider: "When the bundled version of GD is used, this is 1; otherwise, it's set to 0."

Suggested change

	/// When the bundled version of GD is used, this is 1 otherwise it's set to 0.
	/// When the bundled version of GD is used, this is 1; otherwise, it's set to 0.

[Copilot]

[nitpick] The SixLabors.ImageSharp.Drawing package is at 2.1.6 while SixLabors.Fonts is at 2.1.3. Consider aligning minor/patch versions across related SixLabors packages to avoid potential compatibility issues.

Suggested change

	<PackageReference Include="SixLabors.Fonts" Version="2.1.3" />
	<PackageReference Include="SixLabors.Fonts" Version="2.1.6" />