Replace minimp3 with dr_mp3

[DeeJayLSP]

Note: waiting for dr_mp3 to add LAME tags + start delay support, to fix a bug that doesn't happen with minimp3.

Last time minimp3 got updated was in November 2021 (almost 3 years ago).

Meanwhile, dr_mp3, a piece of work done on top of minimp3, has been updated less than a year ago.

Within Godot, the main differences are:

• No need for patches
• No more MSVC warnings (removed system header treatment)
• Possibility of overriding memory allocations (using memalloc)

Template release binary sizes remain the same.

Since minimp3 is removed, the following are also changed in this PR:

• minimp3 module renamed to mp3
• minimp3_extra_formats build variable renamed to mp3_extra_formats

This should not break compatibility unless module/build option name changes count (does not affect existing projects™).

[DeeJayLSP]

Fixed an issue that caused single channel MP3 files to play badly.

This fix could also be applied to #80160 if it was viable

[DeeJayLSP]

It seems like the change adds a 0.05-0.07s silence at the beginning on playback, gonna check if there's a way to fix this.

Edit: this seems like an issue of dr_mp3 itself. See mackron/dr_libs#263 for more info.
Until fixed and this PR gets updated, this should not be merged.