release-23.1: ts: update server queries to account for system tenant id

[blathers-crl]

Backport 1/1 commits from #109727 on behalf of @Santamaura.

/cc @cockroachdb/release

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Previously, ts queries would consider providing no tenant id and the system tenant id as the same and would return all the aggregated datapoints. This was likely due to the original implementation considering that the system tenant would always want to view all the aggregated data.

This is not the case anymore since the system tenant has the ability to view all the data, system tenant specific data or other tenants data. Therefore this commit adjusts the server query code so that if a system tenant id is provided, it returns data for only the system tenant.

Fixes #108929

Release note (bug fix): adjust ts server queries
to be able to return system tenant only metrics if tenant id is provided, this will fix an issue where some metrics graphs appear to double count.

Some screenshots after the change:
All

System

Tenant

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Release justification: low-risk fix.

[blathers-crl]

Thanks for opening a backport.

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[cockroach-teamcity]

This change is