Support passing yaml parameter files via commandline (#253)

* wip

* rcl_arguments_get_param_files() with char **

Restore version of function that outputs a char **

* _rcl_parse_param_rule() allocates string

Before this commit `rcl_parse_params` was allocating space the size of
the argument, but the space only needs to be as big as the argument
minus the prefix length.

* Debug print before incrementing num files

* Alloc and make sure to dealloc on failure

* fix print of parsed parameter rule

* rcutils types not needed as we dont use rcutils_string_array anymore

* minimal test

* cleanup debug prints

* linter fixup

* add tests for param arguments

* lint tests

* Doc for rcl_arguments_get_param_files_count()

* Shrink parameter files

* const param_prefix_len

* Copy parameter file names

* deallocate parameter files in fini

* free memory after tests pass

rcl/include/rcl/types.h

@@ -97,7 +97,4 @@ typedef rmw_ret_t rcl_ret_t;
 /// Argument is not a valid log level rule
 #define RCL_RET_INVALID_LOG_LEVEL_RULE 1020
 
-/// typedef for rmw_message_raw_t;
-typedef rmw_message_raw_t rcl_message_raw_t;
-
 #endif  // RCL__TYPES_H_