Accept error values of any type in TriblerProcess.set_error

[kozlovsky]

I see a significant number of the following errors in GUI logs on my machine and some test machines:

[tribler-gui PID:17032] 2023-07-10 08:19:50,079 - ERROR - tribler.gui.start_gui(82) - Error binding parameter 7 - probably unsupported type.
Traceback (most recent call last):
  File "tribler\core\utilities\process_manager\utils.py", line 29, in new_method
  File "tribler\core\utilities\process_manager\process.py", line 74, in save
  File "tribler\core\utilities\process_manager\process.py", line 224, in _update
sqlite3.InterfaceError: Error binding parameter 7 - probably unsupported type.

During the handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "tribler\gui\start_gui.py", line 79, in run_gui
  File "tribler\core\utilities\process_manager\manager.py", line 112, in sys_exit
  File "tribler\core\utilities\process_manager\process.py", line 204, in finish
  File "tribler\core\utilities\process_manager\utils.py", line 32, in new_method
  File "tribler\core\utilities\process_manager\process.py", line 74, in save
  File "tribler\core\utilities\process_manager\process.py", line 224, in _update
sqlite3.InterfaceError: Error binding parameter 7 - probably unsupported type.

The "parameter 7" is error_msg in the following SQL query (the parameters are counting from zero):

UPDATE processes
SET row_version = ?, "primary" = ?, canceled = ?, creator_pid = ?, api_port = ?,
    finished_at = ?, exit_code = ?, error_msg = ?
WHERE rowid = ? and row_version = ? and pid = ? and kind = ? and app_version = ? and started_at = ?

It is expected for the TriblerProcess.error_msg to be an str or exception instance, but it seems that in some situations, when the TriblerProcess.set_error method is called, the value of another type is passed into it.

To handle this situation and understand what the actual error is, this PR converts any error_msg value to an str even if it is a value of an unknown type.