Migrate to clap

[JR-1991]

This pull request refactors the CLI subcommand definitions throughout the codebase, replacing the deprecated structopt crate with the modern clap crate and its derive macros. It updates all subcommand enums to use clap::Subcommand and #[arg(...)] attributes, streamlining argument definitions and improving maintainability. Additionally, it introduces a wrapper type for file uploads in the dataset CLI to enhance type safety and parsing, and makes minor improvements to argument validation.

Migration from structopt to clap:

• All CLI subcommand enums (AdminSubCommand, AuthSubCommand, CollectionSubCommand, DatasetSubCommand, FileSubCommand) now use #[derive(Subcommand, Debug)] and replace #[structopt(...)] attributes with #[arg(...)] for argument definitions, improving consistency and compatibility with the latest CLI standards. [1] [2] [3] [4] [5]
• The structopt dependency is removed from Cargo.toml, and all use structopt::StructOpt; imports are replaced with use clap::Subcommand;. [1] [2] [3] [4] [5] [6]

CLI argument improvements and cleanup:

• Command descriptions and argument help texts are streamlined for clarity, and legacy/deprecated attributes are removed or updated for all CLI subcommands. [1] [2] [3] [4] [5]
• Argument validation for mutually exclusive options (e.g., required_unless_present) is updated to match the latest clap syntax, improving error handling and user feedback.

Dataset CLI enhancements:

• A new wrapper type CliUploadFile is introduced for file uploads in DatasetSubCommand, improving type safety and parsing for file arguments. The upload logic is updated to use this wrapper type. [1] [2]

Other minor changes:

• The crate name in Cargo.toml is changed from rust-dataverse to dvcli to better reflect the CLI tool's purpose.