Backend List Map Serialization

shared_credentials_files and other list/map backend config values were serialized incorrectly

Setting shared_credentials_files (or any other list-valued key) in the remote_state.config block produced a broken -backend-config argument:

-backend-config=shared_credentials_files=[/a/creds /b/creds]

OpenTofu and Terraform both failed to parse this. The same problem affected map-valued keys. Lists and maps are now written as single-line HCL (["/a/creds","/b/creds"] and {key="value"}), and strings inside them are quoted so embedded quotes, newlines, and tabs survive the round trip.

Thanks to @Rahul-Kumar-prog for contributing this fix!