[FEATURE] Support for ALTERING options of existing flint indices.

[vamsi-amazon]

Is your feature request related to a problem?
Today, once an index is created, there is no way to alter the index options. The ask from this issue is to provide a way to alter options on existing indices.

What solution would you like?
I would like to introduce a new ALTER command for all types of indices.

Examples

• For Skipping Index : ALTER SKIPPING INDEX ON <object> WITH ( options )
• For Covered Index : ALTER INDEX name ON <object> WITH ( options )
• For MV : ALTER MATERIALIZED VIEW ON WITH ( options )

ALTER will result in cancelling existing job and creating a new index job based on the new parameters.

Can we change all the options available?

• auto_refresh: Yes can be changed.
• refresh_interval: Yes can be changed.
• incremental_refresh: Yes can be changed.
• checkpoint_location: No. Theoretically we can do but the new streaming job would start indexing from the beginning.
• watermark_delay: Yes.
• output_mode: Yes.
• index_settings: No, Index is already constructed.
• extra_options: Yes, since we will be creating a new job, we can creating a stream with new options.