fix(renderer): make each unit has multiple texture bindings per target

[yorkie]

This pull request refactors how texture bindings are managed in the OpenGL renderer codebase. The main change is introducing the new GLTextureUnitBinding class to handle multiple texture targets per texture unit, replacing the previous approach that stored only one binding per unit. This makes the texture binding logic more robust and extensible, and also updates the logic to only record up to 16 texture units for performance reasons.

[Copilot]

Pull Request Overview

This pull request refactors the OpenGL texture binding management system to support multiple texture targets per texture unit instead of the previous single-binding approach. The changes introduce a new GLTextureUnitBinding class that can handle multiple texture types (2D, 2D array, 3D, cube map) simultaneously within each texture unit.

• Introduces GLTextureUnitBinding class to manage multiple texture bindings per unit
• Updates texture recording logic to capture all texture types bound to each unit
• Reduces the number of recorded texture units from 32 to 17 for performance optimization

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
src/renderer/gles/context_storage.hpp	Adds new GLTextureUnitBinding class and updates storage data structures
src/renderer/gles/context_storage.cpp	Updates texture restoration logic to use new binding system
src/renderer/gles/context_host.cpp	Modifies texture recording to capture multiple bindings per unit and reduces unit count
src/renderer/gles/context_app.cpp	Updates texture binding change handler to work with new multi-binding system