The statement

SET GLOBAL innodb_encryption_rotate_key_age=0;

would have the unwanted side effect that ENCRYPTION=DEFAULT tablespaces
would no longer be encrypted or decrypted according to the setting of
innodb_encrypt_tables.

We implement a trigger, so that whenever one of the following is executed:

SET GLOBAL innodb_encrypt_tables=OFF;
SET GLOBAL innodb_encrypt_tables=ON;
SET GLOBAL innodb_encrypt_tables=FORCE;

all wrong-state ENCRYPTION=DEFAULT tablespaces will be added to
fil_system_t::rotation_list, so that the encryption will be added
or removed.

Note: This will *NOT* happen automatically after a server restart.
Before reading the first page of a data file, InnoDB cannot know
the encryption status of the data file. The statement
SET GLOBAL innodb_encrypt_tables will have the side effect that
all not-yet-read InnoDB data files will be accessed in order to
determine the encryption status.

innodb_encrypt_tables_validate(): Stop disallowing
SET GLOBAL innodb_encrypt_tables when innodb_encryption_rotate_key_age=0.
This reverts part of commit 50eb40a2
that addressed MDEV-11738 and MDEV-11581.

fil_system_t::read_page0(): Trigger a call to fil_node_t::read_page0().
Refactored from fil_space_get_space().

fil_crypt_rotation_list_fill(): If innodb_encryption_rotate_key_age=0,
initialize fil_system->rotation_list. This is invoked both on
SET GLOBAL innodb_encrypt_tables and
on SET GLOBAL innodb_encryption_rotate_key_age=0.

fil_space_set_crypt_data(): Remove.

fil_parse_write_crypt_data(): Simplify the logic.

This is joint work with Marko Mäkelä.