pgsql: Remove reset of testtablespace from pg_regress on Windows

Remove reset of testtablespace from pg_regress on Windows

testtablespace is an extra path used as tablespace location in the main
regression test suite, computed from --outputdir as defined by the
caller of pg_regress (current directory if undefined).

This special handling was introduced as of f10589e to be specific to
MSVC, as we let pg_regress' Makefile handle this cleanup in other
environments.  This moves the cleanup to the MSVC script running
regression tests instead where needed: check, installcheck and
upgradecheck.  I have also checked this patch on MSVC with repeated runs
of each target.

Author: Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/20200219.142519.437573253063431435.horikyota.ntt@gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/2b2a070d98b2f2c7ecc031e582cfefa400316ce3

Modified Files
--------------
src/test/regress/pg_regress.c | 22 ----------------------
src/tools/msvc/vcregress.pl   | 17 +++++++++++++++--
2 files changed, 15 insertions(+), 24 deletions(-)