Add a "timezone" prop to heatmaps, time series and anomaly charts

What does this MR do?

Chart related implementation of #214370 (closed)

Allow heatmaps, time series and anomaly charts to accept a timezone prop. Both x axis and tooltip formats have been updated to consider this prop.

No changes are expected in the UX as local timezone is used by default.

• In follow-up issue #219210 (closed), other charts should be updated but they need to format their dates as well!
• In a follow-up MR, I will connect the use configuration to the dashboard_panel to wire the solution.

Most loc changes are in time_series_spec.js that were due for a refactor anyway.

How to test

Add :timezone="'UTC'" to the settings of the charts:

diff --git a/app/assets/javascripts/monitoring/components/dashboard_panel.vue b/app/assets/javascripts/monitoring/components/dashboard_panel.vue
index a23d6692e33..221ff21d7be 100644
--- a/app/assets/javascripts/monitoring/components/dashboard_panel.vue
+++ b/app/assets/javascripts/monitoring/components/dashboard_panel.vue
@@ -373,6 +373,7 @@ export default {
       :is="basicChartComponent"
       v-else-if="basicChartComponent"
       :graph-data="graphData"
+      :timezone="'UTC'"
       v-bind="$attrs"
       v-on="$listeners"
     />
@@ -386,6 +387,7 @@ export default {
       :project-path="projectPath"
       :thresholds="getGraphAlertValues(graphData.metrics)"
       :group-id="groupId"
+      :timezone="'UTC'"
       v-bind="$attrs"
       v-on="$listeners"
       @datazoom="onDatazoom"

Screenshots

On my local machine, at 7PM (China time), the time format changes depending on the settings:

:timezone="'UTC'" (local clock in Shanghai)	:timezone="'LOCAL'" (local clock in Shanghai)	:timezone="'LOCAL'" (local clock in Los Angeles)

Anomaly chart verification

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team