feature/update mex-common 0.51.0

[cutoffthetop]

PR Context

• massive clean-up of mapping types and validity
• some type-ignores were left in for future generations to enjoy

Changes

• update mex-common to version 0.51.0
• use proper mapping models
• move inline test mappings to /assets with suffix _mock

Removed

• remove mex.extractors.mapping model in favor of load_yaml and model_validate

Fixed

• fix setValues listyness of test mappings
• fix test mapping schema path
• fix test mapping indentations

[esinsj]

I can't test the code because the changes are not implemented in mex-assets yet ("No such file or directory: '...\mex-assets\mappings\blueant\activity.yaml'")
Otherwise the code looks fine visually.