Update to clap 3.1.0

[dtolnay]

This PR fixes the deprecation errors I saw in the CI of #10394.

Clap 3.1.0 introduced some new deprecations: https://github.com/clap-rs/clap/releases/tag/v3.1.0

warning: use of deprecated struct `clap::App`: Replaced with `Command`
  --> src/cargo/util/command_prelude.rs:25:22
   |
25 | pub type App = clap::App<'static>;
   |                      ^^^
   |
   = note: `#[warn(deprecated)]` on by default

warning: use of deprecated variant `clap::AppSettings::DontCollapseArgsInUsage`: Replaced with `Command::dont_collapse_args_in_usage` and `Command::is_dont_collapse_args_in_usage_set`
   --> src/cargo/util/command_prelude.rs:284:75
    |
284 |     App::new(name).setting(AppSettings::DeriveDisplayOrder | AppSettings::DontCollapseArgsInUsage)
    |                                                                           ^^^^^^^^^^^^^^^^^^^^^^^

warning: `cargo` (lib) generated 2 warnings
warning: use of deprecated variant `clap::AppSettings::NoBinaryName`: Replaced with `Command::no_binary_name`
   --> src/bin/cargo/cli.rs:290:43
    |
290 |                     .setting(AppSettings::NoBinaryName)
    |                                           ^^^^^^^^^^^^
    |
    = note: `#[warn(deprecated)]` on by default

warning: use of deprecated variant `clap::AppSettings::AllowExternalSubcommands`: Replaced with `Command::allow_external_subcommands` and `Command::is_allow_external_subcommands_set`
   --> src/bin/cargo/cli.rs:411:32
    |
411 |                 | AppSettings::AllowExternalSubcommands
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::DisableColoredHelp`: Replaced with `Command::disable_colored_help` and `Command::is_disable_colored_help_set`
   --> src/bin/cargo/cli.rs:416:38
    |
416 |         .global_setting(AppSettings::DisableColoredHelp)
    |                                      ^^^^^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::TrailingVarArg`: Replaced with `Command::trailing_var_arg` and `Command::is_trailing_var_arg_set`
 --> src/bin/cargo/commands/bench.rs:6:31
  |
6 |         .setting(AppSettings::TrailingVarArg)
  |                               ^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::SubcommandRequiredElseHelp`: Replaced with `Command::subcommand_required` combined with `Command::arg_required_else_help`
 --> src/bin/cargo/commands/config.rs:8:37
  |
8 |         .setting(clap::AppSettings::SubcommandRequiredElseHelp)
  |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::Hidden`: Replaced with `Command::hide` and `Command::is_hide_set`
 --> src/bin/cargo/commands/git_checkout.rs:8:31
  |
8 |         .setting(AppSettings::Hidden)
  |                               ^^^^^^

warning: use of deprecated variant `clap::AppSettings::SubcommandRequiredElseHelp`: Replaced with `Command::subcommand_required` combined with `Command::arg_required_else_help`
 --> src/bin/cargo/commands/report.rs:9:37
  |
9 |         .setting(clap::AppSettings::SubcommandRequiredElseHelp)
  |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::TrailingVarArg`: Replaced with `Command::trailing_var_arg` and `Command::is_trailing_var_arg_set`
  --> src/bin/cargo/commands/run.rs:11:31
   |
11 |         .setting(AppSettings::TrailingVarArg)
   |                               ^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::TrailingVarArg`: Replaced with `Command::trailing_var_arg` and `Command::is_trailing_var_arg_set`
  --> src/bin/cargo/commands/rustc.rs:10:31
   |
10 |         .setting(AppSettings::TrailingVarArg)
   |                               ^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::TrailingVarArg`: Replaced with `Command::trailing_var_arg` and `Command::is_trailing_var_arg_set`
 --> src/bin/cargo/commands/rustdoc.rs:7:31
  |
7 |         .setting(AppSettings::TrailingVarArg)
  |                               ^^^^^^^^^^^^^^

warning: use of deprecated variant `clap::AppSettings::TrailingVarArg`: Replaced with `Command::trailing_var_arg` and `Command::is_trailing_var_arg_set`
 --> src/bin/cargo/commands/test.rs:9:31
  |
9 |         .setting(AppSettings::TrailingVarArg)
  |                               ^^^^^^^^^^^^^^

warning: use of deprecated field `clap::Error::kind`: Replaced with `Error::kind()`
  --> src/bin/cargo/cli.rs:36:16
   |
36 |             if e.kind == clap::ErrorKind::UnrecognizedSubcommand {
   |                ^^^^^^

warning: use of deprecated field `clap::Error::info`: Replaced with `Error::context()`
  --> src/bin/cargo/cli.rs:38:27
   |
38 |                 let cmd = e.info[0].clone();
   |                           ^^^^^^

warning: `cargo` (bin "cargo") generated 13 warnings

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r? @alexcrichton

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[Eh2406]

cc #10396