Fix for Sql-Psi SqlCoreEnvironment

[griffio]

Currently sql-psi breaks SqlDelight - main reason is that localFileSystem, jarFileSystem were private.

Make localFileSystem, jarFileSystem protected as they are inherited properties in SqlDelight.
Unless there is some reason due to Isolation for these to be private ?

Fix SqlDelight fixture tests with file.toAbsolutePath as the relative path breaks all tests in SqlDelight.

Note:
SqlDelight will require some minor changes to take this sql-psi version as it is not a compatible version, that will be done once this new version is published and can be tried out.

This sql-psi was tested in SqlDelight by updating settings.gradle

includeBuild('../sql-psi') {
  dependencySubstitution {
    substitute(module("app.cash.sql-psi:core")).using(project(":core"))
    substitute(module("app.cash.sql-psi:environment")).using(project(":environment"))
  }
}

Integration tests are independent builds so need a different relative path for settings.gradle

includeBuild('../../../../../sql-psi') {
  dependencySubstitution {
    substitute(module("app.cash.sql-psi:core")).using(project(":core"))
    substitute(module("app.cash.sql-psi:environment")).using(project(":environment"))
  }
}

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• CHANGELOG.md's "Unreleased" section has been updated, if applicable.

[JakeWharton]

I have no context on this, but if it unblocks upgrading I'm all for it.