[Veditha08]

🛠 Summary

Fixes #4717

The MediaPipe session calculator's local stou32() implementation used std::stoul() without checking whether the entire input string was consumed. This allowed malformed values such as "12abc" and "3.9" to be silently accepted as valid model versions.

Changes:

• Reuses the shared ovms::stou32() parser.
• Rejects explicitly supplied malformed or empty servable_version values with InvalidArgument.
• Preserves the default version 0 when servable_version is omitted.
• Removes the duplicate local parsing implementation.

🧪 Checklist

• Unit tests added.
• The documentation updated (not required for this internal validation fix).
• Change follows security best practices.

Test results:

• MediaPipe version validation tests: 5/5 passed.
• StringUtils tests: 16/16 passed.
• Calculator library build successful.
• clang-format 6.0.1 check passed.
• git diff --check passed.