feat: support invisible columns

[systay]

Description

Adds supports for invisible columns. An invisible column is normally hidden to queries, but can be accessed if explicitly referenced.

As an illustration of when invisible columns may be useful, suppose that an application uses SELECT * queries to access a table, and must continue to work without modification even if the table is altered to add a new column that the application does not expect to be there. In a SELECT * query, the * evaluates to all table columns, except those that are invisible, so the solution is to add the new column as an invisible column. The column remains “hidden” from SELECT * queries, and the application continues to work as previously. A newer version of the application can refer to the invisible column if necessary by explicitly referencing it.

Related Issue(s)

Fixes #14367

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on the CI
• Documentation was added or is not required

[vitess-bot]

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[harshit-gangal]

backport question on issue: #14367 (comment)

[harshit-gangal]

I do not think we need this information in proto. possibly we directly use the proto struct so there might be not a better alternative here.

[harshit-gangal]

I checked, looks like It does not need to be part of proto.

[dbussink]

@harshit-gangal I wonder though, do we need it in the proto for older versions? Or could we also fix it there without that?

[systay]

I think that we should be consistent and allow this setting in the proto until we deprecate the manual specifying of column information in the vschema.

[harshit-gangal]

currently due to authoritative column information provided by vschema proto, we might keep this information and use it if provided. so let's keep this field till we do not deprecate this in vschema.