refactor: replace flot with highcharts (ietf-tools#4030)

* chore: Replace flot with highcharts

Since flot hasn't been updated since 2014 and was only used in one
place. Simplify how highcharts is initialized and used, and re-enable
pre-bs5 export functionality.

* Fix tests

* Remove some console.log statements

Author: larseggert

.pnp.cjs

@@ -0,0 +1,13 @@
+import Highcharts from "highcharts";
+
+import Highcharts_Exporting from "highcharts/modules/exporting";
+import Highcharts_Offline_Exporting from "highcharts/modules/offline-exporting";
+import Highcharts_Export_Data from "highcharts/modules/export-data";
+import Highcharts_Accessibility from"highcharts/modules/accessibility";
+
+Highcharts_Exporting(Highcharts);
+Highcharts_Offline_Exporting(Highcharts);
+Highcharts_Export_Data(Highcharts);
+Highcharts_Accessibility(Highcharts);
+
+window.Highcharts = Highcharts;

.yarn/cache/flot-npm-4.2.2-77eb146093-81910f7bc2.zip

@@ -0,0 +1,13 @@
+import Highcharts from "highcharts/highstock";
+
+import Highcharts_Exporting from "highcharts/modules/exporting";
+import Highcharts_Offline_Exporting from "highcharts/modules/offline-exporting";
+import Highcharts_Export_Data from "highcharts/modules/export-data";
+import Highcharts_Accessibility from"highcharts/modules/accessibility";
+
+Highcharts_Exporting(Highcharts);
+Highcharts_Offline_Exporting(Highcharts);
+Highcharts_Export_Data(Highcharts);
+Highcharts_Accessibility(Highcharts);
+
+window.Highcharts = Highcharts;