[FIX] chart: fix trend line axis alignment

Task Description

Following #5282, we
now have the trend line data as an array of Point, and try to align
the trend line axis to the real x-axis. This can't be done for
categorical axis and time axis without treating the trend axis as
a category axis, for both.

This PR aims to fix the axis for the datetime data, where the axis
was considered as a datetime axis but can't be anymore. As this is
caused by the way chartJs decides to align the axis, we don't have
any other solution, neither have we a possibility to test the fix.

closes #5442

Task: 0
X-original-commit: 80c7840
Signed-off-by: Rémi Rahir (rar) <[email protected]>

src/helpers/figures/charts/runtime/chartjs_scales.ts

@@ -111,11 +111,12 @@ export function getLineChartScales(
       ...(scales.x as any),
       display: false,
     };
-    if (axisType === "category") {
+    if (axisType === "category" || axisType === "time") {
       /* We add a second x axis here to draw the trend lines, with the labels length being
        * set so that the second axis points match the classical x axis
        */
       const maxLength = Math.max(...trendDatasets.map((trendDataset) => trendDataset?.length || 0));
+      scales[TREND_LINE_XAXIS_ID]!["type"] = "category";
       scales[TREND_LINE_XAXIS_ID]!["labels"] = range(0, maxLength).map((x) => x.toString());
       scales[TREND_LINE_XAXIS_ID]!["offset"] = false;
     }