[next-major] Remove traces of CamelCase

As libzim uses CamelCase, we sometimes followed the convention to stick to the pure-wrapper way.
Given case is not that important and we don't follow it everywhere (it's become minor overtime), we should just remove the remaining traces and use snake case everywhere.

It's a tiny change but obviously breaks the API so should not be merged until approaching next major release

# writer
    def config_nbworkers(self, nbWorkers: int) -> Self: ...  # noqa: N803
    def set_mainpath(self, mainPath: str) -> Self: ...  # noqa: N803
    def add_redirection(
        self,
        path: str,
        title: str,
        targetPath: str,  # noqa: N803
        hints: dict[Hint, int],
    ) -> None: ...
    def add_alias(
        self,
        path: str,
        title: str,
        targetPath: str,  # noqa: N803
        hints: dict[Hint, int],
    ) -> None: ...
# suggestion
    def getEstimatedMatches(self) -> int: ...  # noqa: N802
# search
    def getEstimatedMatches(self) -> int: ...  # noqa: N802
    def getResults(self, start: int, count: int) -> SearchResultSet: ...  # noqa: N802

Start from the Python wrapper declarations shown in the issue and locate the remaining CamelCase names in the writer, suggestion, and search APIs. Rename those exposed methods and parameters to snake_case, remove the associated naming exceptions, and verify that references and checks use the new API before the next major release.