API / CoW: constructing Series from Series creates lazy copy (with default copy=False)
xref https://github.com/pandas-dev/pandas/issues/48998 (bullet point about constructors)

In the CoW proposal, the idea for constructors would be that those follow the lazy copy with CoW approach as well, just like other methods and indexing operations that create a new Series/DataFrame from another Series/DataFrame.  
That was not yet implemented in the initial implementation, and this PR is adding it for the `Series(series)` case.

Currently, the way I implemented this is by making a shallow copy of the manager. This however also affects the default (non-CoW) behaviour -> see https://github.com/pandas-dev/pandas/issues/49523. 
Depending on whether we are OK with changing ("fixing"?) that behaviour in 2.0 or not, I can leave this as is, or otherwise put the copy behind a `if get_cnofig("mode.copy_on_write")` check.

- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

I updated this to put the actual code change behind a "if CoW" check (so this PR only changes something for the case of CoW enabled), and will do a separate PR to address https://github.com/pandas-dev/pandas/issues/49523 (and for both Series and DataFrame). > will do a separate PR to address #49523 (and for both Series and DataFrame).

Opened https://github.com/pandas-dev/pandas/pull/50539 for this