Fix string concatenation when build oracle table/relation command text

[MingMZ]

Fixes #113

Reason for fix is to correct string concatenation of command text in OracleDbAdapter.cs.

I also renamed Checkpoint to Respawner in OracleTests.cs; added test cases when include/exclude {schema}.{table}.

[jbogard]

Were you able to make the tests pass?

[MingMZ]

I did run oracle test, with podman spin up an oracle instance.

dotnet test .\Respawn.DatabaseTests\ --nologo --filter OracleTests --results-directory test-results
  Determining projects to restore...
  All projects are up-to-date for restore.
  Respawn -> C:\Projects\Respawn\Respawn\bin\Debug\netstandard2.1\Respawn.dll
  Respawn.DatabaseTests -> C:\Projects\Respawn\Respawn.DatabaseTests\bin\Debug\net6.0\Respawn.DatabaseTests.dll
Test run for C:\Projects\Respawn\Respawn.DatabaseTests\bin\Debug\net6.0\Respawn.DatabaseTests.dll (.NETCoreApp,Version=v6.0)

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.

Passed!  - Failed:     0, Passed:    13, Skipped:     0, Total:    13, Duration: 2 m 26 s - Respawn.DatabaseTests.dll (net6.0)

Forgot to mention, unsure of the reason, I left #if !ORACLE preprocessor unchanged in OracleTests.cs.