Release 2.0.15

Enhance SimpleConsoleFormatter structured state handling

Refactor `SimpleConsoleFormatter` to improve how structured state
is rendered in log messages. For non-exception logs, structured
state is now displayed inline with the log message, separated by
a pipe (`|`) and optionally formatted with ANSI color codes. For
exception logs, structured state and exception details are printed
on separate `[Ex]` lines for clarity.

Updated the constructor to properly initialize the base class
`ConsoleFormatter` with the `FormatterName` constant. Improved
null safety by using a null-coalescing operator (`??`) for the
`_options` field initialization.

Removed outdated logic and comments related to the old structured
state handling to streamline the implementation.