AudioStreamWAV::save_to_wav adding extra '.wav' to file if existing ext is not lower case

[nikitalita]

Tested versions

Tested on current master @ dbad9c60fbc294057172a112e5d8a39d31c210d5
Affects all versions back to 1.0.

System information

macOS 14.5.0, M2 Pro, Vulkan

Issue description

AudioStreamWAV::save_to_wav adds an extra '.wav' to file if existing ext is not lower case. This is because it only does a string literal comparison to the lower-case '.wav' without normalizing the existing extension.

Steps to reproduce

run save_to_wav() with an uppercase .WAV path (e.g. "sound.WAV")
Observe that adds an extra '.wav' to the output file (e.g. "sound.WAV.wav")

Minimal reproduction project (MRP)

N/A