CLN: some cleanups in Series.apply & related
Some cleanups:

* Move the `convert_dtype` warning from `Series.apply` to `SeriesApply`
* Add `*, ` to force use use of keywords
* Set the default for `convert_dtype` in `SeriesApply` to `no_default`
* Drop setting `convert_dtype` internally in `Series.agg`  & `Series.transform` (these are noops, i.e. have no effect)

Thanks @topper-123  it looks like this caused a performance regression https://asv-runner.github.io/asv-collection/pandas/#join_merge.ConcatDataFrames.time_c_ordered?p-axis=0

could you take a closer look? I've bisected this and the regression is actually caused by https://github.com/pandas-dev/pandas/pull/52685. thx, this pr looked weird, but didn't have time to investigate more. The other makes more sense