pkg/query: Return invalid argument if merging non-delta profiles with time range

[metalmatze]

This shouldn't be allowed. In fact, our UI will never do such queries, it's just that the backend is still fine with this.

[alwaysmeticulous[bot]]

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_{Last updated for commit 04a9baa. This comment will update as new commits are pushed.}

[metalmatze]

Some tests fail with rpc error: code = InvalidArgument desc = merge queries with different timestamps are only supported for delta profiles. We should update these tests. I'll take a look.

[metalmatze]

However, we don't want to enforce it at the API level. Closing.