vim: Add support for `ap` and `ip` paragraph text objects (#7687)

This PR adds support for `ap`/`ip` text objects in Vim mode and allows
users to perform paragraph-based operations.

Cases where compatibility with Neovim's behavior is checked, cases where
there are known differences in behavior with Neovim (cases where the
landing position is other than the beginning of the line), and cases
where the Neovim behavior in the test suite seems strange are separated
in the test code so that they can be identified.

Release Notes:

- Added support for `ap` and `ip` paragraph text objects in Vim mode
([#7359](https://github.com/zed-industries/zed/issues/7359)).