Fix SDK initialization and packaging issues in plugin version from FAB

[tustanivsky]

This PR fixes SDK initialization and packaging issues on Windows for the plugin version downloaded from the Unreal Marketplace (FAB).

Context: Epic Games obfuscates any extra files placed in the Binaries directory after pre-building the plugin for publishing while the Sentry SDK expects those files to be present there. To work around this additional file copying is performed during PostBuildSteps that are specified in Sentry.uplugin.

The issue was caused by following factors:

• Legacy path to the Crashpad executable was still being used
• crashpad_wer.dll wans't copied at all
• xcopy command was reporting success but not actually copying files due to mixed path separators

Key changes:

• Added path conversion from forward slashes to backslashes for all Windows batch operations
• Replaced xcopy with directory wildcards to explicit copy commands for individual files
• Split operations into separate commands for better readability and debugging

Closes #1107