New-style Optimizer Hints: milestone 3.3

Hint Pushdown into VIEWs

MySQL doesn't allow hints from outside the view to control what happens inside (what we're calling "Hint Pushdown into VIEWs").
It also doesn't allow hints inside VIEWs (see MDEV-33281 description for detail).

TiDB allows "hint pushdown into VIEWs": https://docs.pingcap.com/tidb/stable/optimizer-hints/ .

When in CREATE VIEW statement, one can use hints. One can use SEL_n to refer to SELECTs inside the VIEW (SEL_1 being the VIEW's first select, etc).

When using the VIEW, one can not use SEL_n to refer to SELECTs inside the VIEW.

Instead, one can use QB_NAME to assign a name to a SELECT inside a VIEW by specifying a path to it (see the attached doc)

Design Doc:

https://docs.google.com/document/d/1OuVnP9zgl0LHcYvjXuu34XHBBuTI6yEk0qNT-iAvcKY/edit?usp=sharing

Research Doc:

https://docs.google.com/document/d/1fDX3wWS2cYwp6P2ikgGYkHJhE7dSQEI0apNvkn4lBCc/edit?usp=sharing