Improve float to int audio conversion (fixes #21330 and #24683)

[bakajikara]

Resolves: #21330
Resolves: #24683

• Adds std::clamp to prevent overflow.
• Ensures silence (0.0f) correctly maps to 0.
• Implements correct rounding instead of truncation.
• TargetBits can be specified independently of the container type (would also be useful for converting to 24-bit).

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

[zacjansheski]

Tested on MacOS 15, Windows 11, Ubuntu 22.04.3. Approved
#21330 FIXED
#24683 FIXED