chore(metrics): remove create alert and create widget actions

[obostjancic]

• Replaces closed chore(metrics): remove create alert and create widget actions #78596
• Part of DDM Beta end #77547
• Hides Metric Alert & Widget creation flows

Without custom metrics flag:

[codecov]

Codecov Report

Attention: Patch coverage is 22.80702% with 44 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...tatic/app/views/metrics/metricQueryContextMenu.tsx	20.58%	27 Missing ⚠️
static/app/views/metrics/pageHeaderActions.tsx	31.25%	11 Missing ⚠️
static/app/views/metrics/metricsBetaEndAlert.tsx	33.33%	2 Missing ⚠️
...ponents/modals/metricWidgetViewerModal/queries.tsx	0.00%	1 Missing ⚠️
static/app/views/dashboards/dashboard.tsx	0.00%	1 Missing ⚠️
static/app/views/dashboards/widgetCard/index.tsx	0.00%	1 Missing ⚠️
...p/views/settings/projectMetrics/projectMetrics.tsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #78603      +/-   ##
==========================================
- Coverage   78.13%   78.13%   -0.01%     
==========================================
  Files        7098     7098              
  Lines      312860   312869       +9     
  Branches    51103    51103              
==========================================
+ Hits       244463   244470       +7     
- Misses      62020    62022       +2     
  Partials     6377     6377