feat: migrate zlog to zig 0.15.1

[hendriknielaender]

This commit migrates the zlog library from Zig 0.14.1 to 0.15.1, ensuring full compatibility with the latest language features and API changes.

Major Changes

Build System

• Update minimum Zig version to 0.15.1 in build.zig.zon
• Migrate addStaticLibrary() to addLibrary() with .linkage = .static
• Update deprecated root_source_file to root_module pattern
• Upgrade dependencies to Zig 0.15.1 compatible versions

Standard Library Migration

• Replace std.io.getStdErr() with std.fs.File.stderr()
• Migrate std.ArrayList.init() to std.array_list.Managed().init()
• Update std.time.sleep() to std.Thread.sleep()
• Fix writer APIs to use deprecatedWriter().any() pattern
• Replace std.fmt.fmtSliceHexLower() with direct {x} formatting

Core Library Changes

• Replace removed std.BoundedArray with custom bounded array implementations
• Add missing methods (get, capacity, constSlice) to custom data structures
• Update correlation.zig span stack implementation for 0.15.1 compatibility
• Maintain zero-allocation design throughout migration

Benchmark Updates

• Add deprecatedWriter() methods to custom writer structs
• Fix ArrayList and FixedBufferStream writer method calls
• Work around zbench writer API incompatibilities with simple output
• Ensure all benchmark executables build and run successfully

Dependencies

• Upgrade zbench to v0.11.1 (Zig 0.15.0-dev compatible)
• Update libxev dependency hash for 0.15.1 compatibility
• Patch cached libxev build.zig for ArrayList compatibility