Allow to add if not exists statement to create table queries

[Baptouuuu]

Allowing the ShowCreateTable class to generate CREATE TABLE queries suffixed with IF NOT EXISTS enables auto table creation for tools such as formal/migrations

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.33%. Comparing base (7400135) to head (cb87864).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop      #38      +/-   ##
=============================================
+ Coverage      97.28%   97.33%   +0.04%     
- Complexity       633      634       +1     
=============================================
  Files             96       96              
  Lines           4200     4236      +36     
=============================================
+ Hits            4086     4123      +37     
+ Misses           114      113       -1     

Flag	Coverage Δ
	?

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.