gdb/record: rename record_full_list to record_full_log

Now that we no longer use a linked list to manage the history, the name
"record_full_list" is no longer meaningful. This commit changes the name
to record_full_log since it is the execution log. I decided to not say
"record_full_execution_log" to avoid overly long lines when accessing
it.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-By: Christina Schimpe <christina.schimpe@intel.com>
Approved-By: Guinevere Larsen <guinevere@redhat.com>