Add CLI flag for HTTP API token path (VC) (#6577)

* Add cli flag for HTTP API token path (VC)

* Add http_token_path_flag test

* Add pre-check for directory case & Fix test utils

* Update docs

* Apply review: move http_token_path into validator_http_api config

* Lint

* Make diff lesser to replace PK_FILENAME

* Merge branch 'unstable' into feature/cli-token-path

* Applt review: help_vc.md

Co-authored-by: chonghe <44791194+chong-he@users.noreply.github.com>

* Fix help for cli

* Fix issues on ci

* Merge branch 'unstable' into feature/cli-token-path

* Merge branch 'unstable' into feature/cli-token-path

* Merge branch 'unstable' into feature/cli-token-path

* Merge branch 'unstable' into feature/cli-token-path

validator_client/src/cli.rs

@@ -247,6 +247,18 @@ pub fn cli_app() -> Command {
                 .help_heading(FLAG_HEADER)
                 .display_order(0)
         )
+        .arg(
+            Arg::new("http-token-path")
+                .long("http-token-path")
+                .requires("http")
+                .value_name("HTTP_TOKEN_PATH")
+                .help(
+                    "Path to file containing the HTTP API token for validator client authentication. \
+                    If not specified, defaults to {validators-dir}/api-token.txt."
+                )
+                .action(ArgAction::Set)
+                .display_order(0)
+        )
         /* Prometheus metrics HTTP server related arguments */
         .arg(
             Arg::new("metrics")