v1: Use custom Flet exceptions

[FeodorFitsner]

Make sure Flet python package does not throw generic Exceptions.

[ndonkoHenri]

Starter:

flet/sdk/python/packages/flet/src/flet/controls/exceptions.py

Lines 1 to 19 in b996d06

	class FletException(Exception):
	pass
	class FletUnsupportedPlatformException(FletException):
	"""
	Thrown by operations that are not supported on the current platform.
	"""
	def __init__(self, message: str):
	super().__init__(message)
	class FletUnimplementedPlatformEception(FletUnsupportedPlatformException):
	"""
	Thrown by operations that have not been implemented yet.
	"""
	pass