Add a default size to the mapping

[msmakouz]

What was changed

This PR adds default size values to the mapping. The same value as the default value in the methods:
https://github.com/cycle/database/blob/2.x/src/Schema/AbstractColumn.php#L574
https://github.com/cycle/database/blob/2.x/src/Driver/MySQL/Schema/MySQLColumn.php#L329

Why?

Without this change, the size is not set when creating a column by calling the type method:
https://github.com/cycle/database/blob/2.x/src/Schema/AbstractColumn.php#L477

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (bbdb864) 95.10% compared to head (52d2745) 95.10%.

Additional details and impacted files

@@            Coverage Diff            @@
##                2.x     #150   +/-   ##
=========================================
  Coverage     95.10%   95.10%           
  Complexity     1812     1812           
=========================================
  Files           129      129           
  Lines          4987     4987           
=========================================
  Hits           4743     4743           
  Misses          244      244           

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