chore: support sqlalchemy 2.x and flask-sqlalchemy 3 (breaking)

[dpgaspar]

Description

• Added config option to not create FAB's tables FAB_CREATE_DB
• Flask-SQLAlchemy singleton is now created by FAB, import from from flask_appbuilder.extensions import db. This means init now is simpler: appbuilder.init_app(app)
• appbuilder.sm.get_session was renamed to appbuilder.sm.session
• Doing queries now require an app_context (breaking from flask-sqlalchemy)
• SQLAInterface will not swallow exceptions, and accepts an optional parameter to commit or not commit
• appbuilder.get_app does not exist anymore, use current_app instead, you can still use appbuilder.app but it's deprecated

ADDITIONAL INFORMATION

• Has associated issue:
• Is CRUD MVC related.
• Is Auth, RBAC security related.
• Changes the security db schema.
• Introduces new feature
• Removes existing feature

[hasansezertasan]

Related: #2240

[ddorian]

Also related #2038 #2162 #2108 #1940

[jnahmias]

@dpgaspar thank you so much for working on this! I plan on running some tests on this and will report back.
What sort of reviews are you waiting on prior to merging this?

[veinkr]

Hi, @dpgaspar , just curious if there are any new process to upgrade to flask-sqlalchemy>3.0?

[eqperes]

session was removed from arguments but need to be removed from docstring too

[zacqed]

@dpgaspar Is this PR ready for merge and release?

[hectorem2]

I ran Flask-AppBuilder in this branch and it seems everything is fine, there is only the issue of the field_flags attribute, for which I have already submitted the pull request #2294.