[PostgreSQL]Detect full table name using search_path and information_schema

[k1LoW]

Fix #181

[codecov]

Codecov Report

Merging #184 into master will decrease coverage by 1.03%.
The diff coverage is 63.15%.

@@            Coverage Diff             @@
##           master     #184      +/-   ##
==========================================
- Coverage   68.41%   67.37%   -1.04%     
==========================================
  Files          18       18              
  Lines        3112     3148      +36     
==========================================
- Hits         2129     2121       -8     
- Misses        769      813      +44     
  Partials      214      214

Impacted Files	Coverage Δ
schema/schema.go	35.07% <ø> (ø)	⬆️
drivers/postgres/postgres.go	69.63% <63.15%> (-0.94%)	⬇️
datasource/datasource.go	16.75% <0%> (-15.19%)	⬇️

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