traffic_ctl - Add rpc invoke option.

[brbzull0]

Add Input option to invoke a rpc function by specifying the method name and the parameters directly
from the command line.

With this change we now can call any rpc method without the need to support it in traffic_ctl:

$ traffic_ctl rpc invoke get_service_descriptor
--> {"id": "50d9431e-85f9-4999-abc7-4f26ac3cc1e1", "jsonrpc": "2.0", "method": "get_service_descriptor"}
<--  {response}

This also removed CustomizableRequest which is no longer needed(it was unused but left it as base for this case).

[brbzull0]

[approve ci fedora]

[brbzull0]

This #8694 will fix the autest

[brbzull0]

[approve ci autest]

[SolidWallOfCode]

Dang, shouldn't that be std::string const&?

[SolidWallOfCode]

Seems it would be nice to have a --json option where I can pass in the JSON literally.

[brbzull0]

Seems it would be nice to have a --json option where I can pass in the JSON literally.

@SolidWallOfCode You can, the --params will handle that, internally it will use the YAML parser, so you can pass json or yaml:

traffic_ctl rpc invoke read_files_method --params '{ "filenames": [  "file1", "file2" ] }'

or

traffic_ctl rpc invoke read_files_method --params 'filenames: ["file1", "file2"]'

thanks for the review