default to primary tablet if not set in VStream api

[harshit-gangal]

Description

Now the underlying streamExecute uses plan builder to build and execute the query.
The VStream API pass on the tablet type received from the request.

Earlier it was hardcoded to use a PRIMARY tablet but now it uses what the user has passed in the request.
For query-based streaming through MySQL protocol, it is already handled for cases when tablet type is not set.

For direct VStream API calls, the fallback logic is added to use PRIMARY tablet type if not provided.

Related Issue(s)

• Fixes vtgate: regression from v10 to v11 on stream * from queries #8676

Checklist

• Should this PR be backported?
• [] Tests were added or are not required
• Documentation was added or is not required

Deployment Notes

[systay]

@derekperkins any chance that you can check if this solves the problem for you?

[derekperkins]

I can confirm that setting the target to master solves the problem. I haven't tried primary because I thought most of the renaming PRs hit after 11.0.0

[systay]

this needs to be backported!