Fix partition query in Presto

[betodealmeida]

SUMMARY

Our Presto cluster doesn't support SHOW PARTITIONS. Reading the Presto docs, it's unclear to me if Presto supports this at all (cc: @nishantrayan). I changed the query that loads partitions to use the table_name$partitions hidden table instead.

TEST PLAN

SQL Lab is now able to load metadata correctly.

ADDITIONAL INFORMATION

[ ] Has associated issue:
[ ] Changes UI
[ ] Requires DB Migration. Confirm DB Migration upgrade and downgrade tested.
[ ] Introduces new feature or API
[ ] Removes existing feature or API
[X] Fixes bug
[ ] Refactors code
[ ] Adds test(s)

REVIEWERS

@xtinec @datability-io @khtruong @nishantrayan

[codecov-io]

Codecov Report

Merging #7250 into lyftga will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           lyftga    #7250   +/-   ##
=======================================
  Coverage   64.53%   64.53%           
=======================================
  Files         425      425           
  Lines       20861    20861           
  Branches     2280     2280           
=======================================
  Hits        13463    13463           
  Misses       7272     7272           
  Partials      126      126

Impacted Files	Coverage Δ
superset/db_engine_specs.py	57.23% <ø> (ø)	⬆️

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[hustwolf]

nice, i have the same problem, and i want to fix it ,but you already did