Update AJV to 8.1.0

[shuse2]

Description

Update ajv to latest 8.1.0.

There are a lot of breaking changes. Some of the changes observed was

• dataPath is now instancePath with / separated instead of .
• addKeyword have different interface
• must is used instead of should in error message
• id cannot be used anymore. it must be $id
• meta schema format keyword does not work

Official migration documentation is

• https://ajv.js.org/v6-to-v8-migration.html#potential-migration-difficulties

Initial tried changes are here

• 9d25bb3

Also,

addUsedSchema: false,

Check this property added to the Ajv is still necessary or not.