Performance optimization pass and cleanup for #5151

[RyeMutt]

Description

• Replace remaining boost::filesystem usage with std::filesystem
• Add Tracy profiler tagging to LLFile that's disabled by default
• Clean up LLFile and LLFilesystem operations to reduce temporary allocations and utf8->utf16 conversions
• Reduce temporary allocations and repeated utf8->utf16 conversions in LLTextureCache with new LLFile IO code
• Add non-allocating to_chars and to_wchars string creation functions to LLUUID to reduce std::string allocations during path creation
• Fix LLFile::tmpdir failing when temp directory is located in a unicode path on windows
• Add move operators to fsyspath to match copy operator
• Replace LLFile::utf8StringToWstring with our fsyspath std::filesystem::path adapter
• Introduce std::filesystem::path to llifstream/llofstream wrappers
• Restore LLUniqueFile RAII class for FILE* safety to reduce breaking downstream code

Related Issues

Issue Link: #5151

---

Checklist

Please ensure the following before requesting review:

• I have provided a clear title and detailed description for this pull request.
• If useful, I have included media such as screenshots and video to show off my changes.
• The PR is linked to a relevant issue with sufficient context.
• I have tested the changes locally and verified they work as intended.
• All new and existing tests pass.
• Code follows the project's style guidelines.
• Documentation has been updated if needed.
• Any dependent changes have been merged and published in downstream modules
• I have reviewed the contributing guidelines.

---

Additional Notes

[Copilot]

Pull request overview

This PR performs a comprehensive performance optimization pass related to issue #5151, focusing on replacing boost::filesystem with std::filesystem throughout the codebase, reducing temporary allocations and UTF8↔UTF16 conversions, and improving file I/O operations.

Key changes:

• Complete migration from boost::filesystem to std::filesystem across all platforms
• Introduction of TEXT() macro and std::filesystem::path parameter support to LLFile APIs
• Addition of non-allocating LLUUID::to_chars() and to_wchars() methods to reduce string allocations during path construction
• Fix for LLFile::tmpdir() failing with Unicode paths on Windows
• Introduction of LLUniqueFile RAII wrapper for FILE* safety

Reviewed changes

Copilot reviewed 70 out of 70 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
indra/llcommon/llfile.h	Major API refactor: Added std::filesystem::path overloads, TEXT macro for platform-specific mode strings, removed LL_COMMON_API attributes
indra/llcommon/llfile.cpp	Implementation of new path-based APIs, fix for tmpdir() Unicode support on Windows, Tracy profiler integration
indra/llcommon/lluuid.h/cpp	Added to_chars() and to_wchars() for non-allocating UUID string generation
indra/llcommon/fsyspath.h	Added move operators to match copy operator
indra/llfilesystem/*	Complete migration from boost::filesystem to std::filesystem
indra/newview/lltexturecache.*	Optimized to use std::filesystem::path and new LLUUID methods to reduce allocations
indra/test/namedtempfile.h	Migrated from boost to std filesystem, changed getName() return type to const std::filesystem::path&
Multiple fopen call sites	Updated to use TEXT() macro for proper wide-char mode strings on Windows

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Casting to const char* from u8string() is unsafe and may cause issues. The u8string() method returns a std::u8string, and c_str() returns const char8_t*, not const char*. This explicit cast can lead to undefined behavior or incorrect string handling. Consider using the string() method instead or properly handling the u8string type.

Suggested change

	"with open(r'" << (const char*)file.getPath().u8string().c_str() << "', 'wb') as f:\n"
	"with open(r'" << file.getPath().string().c_str() << "', 'wb') as f:\n"

[RyeMutt]

The (const char*)u8string()._c_str() is to engage std::filesystems utf8 conversion machinery...unfortunately c++ still hasn't made that easy to work with.

[akleshchev]

/Users/runner/work/viewer/viewer/indra/llui/llxuiparser.cpp:1400:31: error: use of undeclared identifier 'TEXT'
 1400 |     ScopedFile file(filename, TEXT("rb"));
      |                               ^
1 error generated.

[RyeMutt]

Fixed!