[16.0][IMP] session_db: Modify the way to parse data from session data

[JonathanOsAlc]

Description of the issue/feature this PR addresses:

Current behaviour before PR:

• When the session has a key with a binary value and uses the session_db module, it triggers an error because the binary value can't be written to the database of session_db.
• Also, it trigger error when the value is int or float and Odoo wants to render that value as monetary.
• And when using debug in the URL parameter and the value is a number, for example: URL?debug=1

Desired behavior after PR is merged:

• Add a way to detect the binary values to parse as strings when saving the session to the database.
  • To identify the data, that was converted from binary to str, add a prefix base64:: to the string.
  • Then when the session needs to be read, detect the values modified, and parse again to base64.
• Also verify if some value of session is a monetary value and parse to float type.
• And keep string type in the value of the 'debug' website parameter.

[OCA-git-bot]

Hi @sbidoul,
some modules you are maintaining are being modified, check this out!