TYP: enhance ExcelWriter with generic type support and overloads

[9en9i]

• Closes Generic ExcelWriter #1559
• Tests for ExcelWriter fixed

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I think

Suggested change

	self: ExcelWriter,
	self,

will do

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From the docs only FilePath and BinaryIO are supported

Suggested change

	path: FilePath | WriteExcelBuffer | ExcelWriter,
	path: FilePath | BinaryIO,

Also to other overloads

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Please add default values

Suggested change

	engine: Literal["auto"] | None = ...,
	date_format: str | None = ...,
	datetime_format: str | None = ...,
	mode: Literal["w", "a"] = ...,
	storage_options: StorageOptions = ...,
	if_sheet_exists: ExcelWriterIfSheetExists | None = ...,
	engine_kwargs: dict[str, Any] | None = ...,
	engine: Literal["auto"] | None = None,
	date_format: str | None = None,
	datetime_format: str | None = None,
	mode: Literal["w", "a"] = "w",
	storage_options: StorageOptions = None,
	if_sheet_exists: ExcelWriterIfSheetExists = "error",
	engine_kwargs: Mapping[str, Any] | None = None,

Also to other overloads

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Suggested change

	engine: Literal["openpyxl"] = ...,
	engine: Literal["openpyxl"],

it has to be the fixed literal openpyxl, if I'm not mistaken

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Suggested change

	engine: Literal["odf"] = ...,
	engine: Literal["odf"],

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Suggested change

	engine: Literal["xlsxwriter"] = ...,
	engine: Literal["xlsxwriter"],

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I am confused, maybe we should overload __new__ instead of __init__ here? cc @Dr-Irv @loicdiridollou