Preserve remote URL casing in texture lookup normalization

[binbonn]

Summary

This PR fixes a texture loading issue where <img src="..."> URLs could be lowercased during texture path normalization.
Some remote image paths are case-sensitive, so this could break valid image URLs.

Motivation & Context

Remote URLs and data URIs should preserve their original casing.
The previous normalization path applied lowercase rules intended for local file paths to all texture inputs.

Fixes: #9986

Implementation Details

• Added NormalizeLookupPath in Texture.Load.cs to centralize lookup normalization behavior.
• Kept existing lowercase normalization for local file paths.
• Preserved original casing for:
  • http/https URLs
  • data: URIs
• Applied the same normalization path in both:
  • LoadInternal (load/cache insert path)
  • Find (cache lookup path)

This keeps cache behavior consistent while preventing URL casing regressions.

Screenshots / Videos (if applicable)

N/A (non-visual fix)

Checklist

• Code follows existing style and conventions
• No unnecessary formatting or unrelated changes
• [N/A] Public APIs are documented (if applicable)
• Unit tests added where applicable and all passing
• I’m okay with this PR being rejected or requested to change 🙂

[Copilot]

Pull request overview

This PR fixes texture loading/caching behavior so that remote http/https image URLs and data: URIs are no longer lowercased during texture-path normalization, preventing failures when remote paths are case-sensitive (Issue #9986).

Changes:

• Introduced NormalizeLookupPath to centralize texture cache key normalization.
• Preserved casing for http/https URLs and data: URIs while keeping local file paths normalized/lowercased.
• Applied the same normalization logic in both LoadInternal and Find to keep cache insert/lookup consistent.

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[Copilot]

Pull request overview

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

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