Refactor cli to use clap’s derive. (#1228)

This PR changes how the clients -- krillc, krillta, as well as the
integration tests -- work to better fit the derive model provided by clap.
This results in basically everything in the cli module and all the
integration tests being different now.

The PR slightly changes the options for both krillc and krillta. For krillc,
the --server, --token, --format, and --api options are now before the first
subcommand (since they affect all commands). For krillta, those options are
now after krillta proxy but before the next subcommand, while --format is
now after krillta signer.

This PR also removes client support and integration tests for RTA.

This is a breaking change.

.github/workflows/ci.yml

@@ -46,7 +46,7 @@ jobs:
         # Test against the oldest supported version.
         # Test against beta Rust to get early warning of any problems that might occur with the upcoming Rust release.
         # Order: oldest Rust to newest Rust.
-        rust: [1.70.0, stable, beta]
+        rust: [1.74.0, stable, beta]
 
         # Test with no features, default features ("") and all except UI tests.
         # Order: fewest features to most features.
@@ -68,7 +68,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        rust: [1.70.0, stable, beta]
+        rust: [1.74.0, stable, beta]
         features: ["hsm", "hsm,hsm-tests-kmip"]
     steps:
     - name: Checkout repository
@@ -114,7 +114,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        rust: [1.70.0, stable, beta]
+        rust: [1.74.0, stable, beta]
         features: ["hsm,hsm-tests-pkcs11"]
     steps:
     - name: Checkout repository