[sbc100]

Followup to #27749.

Make all remaining JS libraries compatible with Closure compiler in ES6 module mode (-sEXPORT_ES6).

• Change loop variables in $miniTempWebGLFloatBuffers__postset and $miniTempWebGLIntBuffers__postset from var to let to prevent duplicate top-level var declaration collisions in ES module scope.
• Remove duplicate forward var declarations in $GLEmulation__postset and initialize GLEmulation.fogColor as [].
• Provide default values for optional arguments across libbrowser.js, libglfw.js, libhtml5.js, libopenal.js, libsdl.js, libwasmfs.js, libfs_shared.js, libworkerfs.js, libproxyfs.js, and liblz4.js.
• Remove surplus argument passed to GL.postDrawHandleClientVertexAttribBindings in libwebgl.js.
• Remove unused parameter from GLImmediate.createRenderer.
• Define source: null on SDL.music in libsdl.js.
• Avoid this.socketEvent receiver collapse warning in libwebsocket.js.
• In libcore.js, fix missing typeof check for globalThis.performance?.now.
• Only generate FS_<symbol> function aliases in libfs.js for lowercase function properties.
• Update test_closure_full_js_library to run with -sEXPORT_ES6 and remove temporary test_closure_fs_es6.

See: #27747

[gemini-code-assist]

Code Review

This pull request introduces significant updates to the library files to improve ES6 compatibility and default parameter handling, including the transition to ES6 module output in tests. A critical issue was identified in src/lib/libglemu.js where initializing materialShininess to an empty array [] changes its truthiness and could lead to runtime errors; the reviewer suggests using a safe default value like [0.0] instead.