Pydantic V2 blog (#4218)

* first draft of pydantic V2 blog

* more blog

* blog rendering and formatting

* more section

* completing conversion table

* prompt build

* reviewing blog post

* more reviewing and extending

* recommendations from @Rabscuttler and @PrettyWood

* add implementation details and more suggestions

* comment about breaking changes

* convert namespae to table, more removals

* Apply suggestions from code review by @tiangolo

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

* feedback from @tiangolo's review

* changes from @adriangb's review

* Apply suggestions from code review

Co-authored-by: Zac Hatfield-Dodds <zac.hatfield.dodds@gmail.com>

* convert namespace info to psuedo-code

* rename property, remove schema_json()

* adding validation context

* remove 'model_schema_json', take 2

* more tweaks while reviewing

* comment about pypy and tagged unions

* add thanks :prey:, prepare for release

* suggestions from @PrettyWood

* suggestions from @PrettyWood, model_dump_json comment

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>
Co-authored-by: Zac Hatfield-Dodds <zac.hatfield.dodds@gmail.com>