Replace escape-latex package with inline ESM implementation

[andreialecu]

Summary

• Replaces the CommonJS-only escape-latex dependency with an inline ESM module
• Eliminates the "Module 'escape-latex' is not ESM" warning in Angular and other ESM-first bundlers
• Enables proper tree-shaking of this code

Part of #3649

Details

The escape-latex package hasn't been updated in 7+ years and only ships CommonJS. Rather than waiting for an upstream ESM build, this inlines a minimal implementation that only includes what mathjs needs.

The implementation produces identical output to the original escape-latex package v1.2.0.

Test plan

• New unit tests for the escapeLatex module (all special characters, formatting escapes, edge cases, stack overflow regression)
• Existing latex.test.js tests pass
• All 6666 unit tests pass
• Lint passes with zero warnings