Heatmaps do not show full time range when using timestamp on an axis

## Expected Behavior

The heatmap chart visualizes the full time range of the query when a time value is selcted for a heatmap axis, similar to the behavior of a bar chart (example below) using a time value.

## Current Behavior

The heatmap chart instead only shows the range of the data. All of the images I've included in this issue are representing the same data with the same time range query (7 days, but data only exists in the last 24 hours).

Timestamp as "row":

Timestamp as "column":

## Possible Solution

## Steps to Reproduce (for bugs)

1. Build a heatmap with one axis using the "timestamp" value using a query that returns some data
2. Run a query to populate that heatmap using a timerange that exceeds the available data for that query
3. Observe that the chart does not reflect that time range where no data was available

## Context

The heatmap can be a valuable storytelling widget but by "trimming" the visualization users may not understand the true context of the events over time.

## Your Environment

* Graylog Version: 7.0.3
* Java Version:
* OpenSearch Version:
* MongoDB Version:
* Operating System:
* Browser version:

## Checklist
[] This issue fix need to be backported.
[] Does this issue have **security** implications?