Remove src\TestSupport\TestCommandTrait::class from yiisoft/db.

[terabytesoftw]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌

[what-the-diff]

• Add composer.dev.json to load tests
• Update composer config for yiisoft/db package
• Remove test command trait from db package and use it in this repo instead of the one provided by db package itself (because we need to add some additional methods)
• Fix phpunit configuration: remove code coverage, fix colors option value, set execution order as default because random is not supported on Windows yet https://github.com/sebastianbergmann/phpunit-documentation-english/issues/906#issuecomment-624098981
• Use source installation mode for yiisoft\db dependency so that all its dependencies are installed with sources too (to make infection work). This also requires using merge plugin which was added into extra section of root composer file before running update command below
• Rename tests/Fixture to tests/Support
• Add TestTrait trait for test cases
• Change sql query in batchInsert method of CommandProvider class (add SELECT 1 FROM SYS.DUAL)

[codecov]

Codecov Report

Base: 92.26% // Head: 92.70% // Increases project coverage by +0.44% 🎉

Coverage data is based on head (4a29972) compared to base (dd1ccb0).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 4a29972 differs from pull request most recent head 50e7351. Consider uploading reports for the commit 50e7351 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #108      +/-   ##
============================================
+ Coverage     92.26%   92.70%   +0.44%     
- Complexity      194      195       +1     
============================================
  Files            15       15              
  Lines           517      521       +4     
============================================
+ Hits            477      483       +6     
+ Misses           40       38       -2     

Impacted Files	Coverage Δ
src/CommandPDO.php	98.18% <100.00%> (+7.27%)	⬆️
src/DDLQueryBuilder.php	78.78% <100.00%> (+2.92%)	⬆️
src/Schema.php	97.29% <100.00%> (ø)
src/ConnectionPDO.php	91.66% <0.00%> (-5.56%)	⬇️

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