Use analyzed expression trees for constraint construction.

[arssher]

Initially I planned this as an easy change which would

• Allow to use weird types such as bytea as hash partitioning key --
  currently we can't do that because hashvarlena declared as accepting
  'internal' type, and analyzer can't pass bytea to it.
• Make everything a bit simpler, because expression is analyzed anyway
  (cook_partitioning_expression), so a bit of code unification was expected.

Eventually it turned out to be much more cumbersome for various reasons (e.g.
analyzed trees should be adapted for childs due to dropped columns), so I am not
even sure it is worthwhile anymore.

Also, micro bug fix at partition_filter.c

[codecov-io]

Codecov Report

Merging #163 into master will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #163 +/- ## ======================================= Coverage 91.74% 91.74% ======================================= Files 43 43 Lines 6384 6384 ======================================= Hits 5857 5857 Misses 527 527

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update dd072e5...dd71813. Read the comment docs.

[arssher]

Suspended.