[2.x] Load default migrations for this package if DX decides not to publish/modify them.

[r-kujawa]

What does this PR do? 🤖

• loadMigrationsFrom() automatically if DX does not feel the need to make any modifications.
• Remove legacy workaround code that used to publish the migration.

Does this relate to any issue? 🔗

Closes #25

[codecov]

Codecov Report

Patch coverage: 80.00% and project coverage change: +11.49 🎉

Comparison is base (b8e3dfb) 55.12% compared to head (a0c8d11) 66.61%.

Additional details and impacted files

@@              Coverage Diff              @@
##             master      #31       +/-   ##
=============================================
+ Coverage     55.12%   66.61%   +11.49%     
+ Complexity      222      221        -1     
=============================================
  Files            42       42               
  Lines           702      701        -1     
=============================================
+ Hits            387      467       +80     
+ Misses          315      234       -81     

Impacted Files	Coverage Δ
src/Console/Commands/Install.php	100.00% <ø> (+1.66%)	⬆️
src/PaymentServiceProvider.php	96.42% <80.00%> (+3.83%)	⬆️

... and 1 file with indirect coverage changes

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