chore: deprecate restricted metrics (#8197)

* chore: deprecate restricted metrics

An early community contribution added the concept of restricted metrics.

The idea was to allow for some metrics to be restricted, and if a metric
was tagged as such, a user would need to be given access to that metric
more explicitely, through a special perm we would maintain for that
metric.

Now since the new concept of "Adhoc Metrics", the popover that lets a
user pick a column and an aggregate function or to write their own SQL
expression inline, this restriction is completely bypassed. Adhoc
metrics was developed without the restricted metrics in mind.

Anyhow, in the near future, we'll be rethinking the ideas behind
data-access permissions, and things like column-level or row-level
security will be redesigned from scratch.

By deprecating this feature, we're removing a confusing and mostly broken
feature, and making it easy to move forward

* Use context manager to drop columns

* disable jest's maxWorkers

superset/exceptions.py

@@ -36,10 +36,6 @@ class SupersetSecurityException(SupersetException):
         self.link = link
 
 
-class MetricPermException(SupersetException):
-    pass
-
-
 class NoDataException(SupersetException):
     status = 400