ResolutionResultApiIntegrationTest.groovy

This is just a refactoring of tests, to make it clearer: the base

package started to grow significantly.

This commit refactors how conflict resolution selection reasons are handled, in order to:

- collect the list of versions which participated in conflict resolution

- report a single conflict resolution cause when conflicts are resolved several times for the same module

- consistently report module replacement rules as rules, not conflict resolution. Before this change,

a module replacement was reported as both a conflict and a rule

This is similar to the fix in #4301, but this time for direct dependencies

instead of constraints.

The configuration is purely internal for now, and primarily aimed at making

the tests faster to execute.

Replaces injecting a property in the gradle.properties with injecting

the gradle.enableFeaturePreview in settings.gradle

Before this fix, whenever a constraint used a custom message, there were 2

separate descriptors in the list of descriptors in the selection reason: one

was `REQUESTED` with the custom message and one `CONSTRAINT`.

After this commit, the custom message is properly attached to the `CONSTRAINT`

descriptor instead. We also make sure that regular constraints do not lead to

an additional "REQUESTED" descriptor being added.

This commit adds test coverage, using the new resolve test fixtures.

Signed-off-by: Cedric Champeau <cedric@gradle.com>

This commit adds tests that show that the resolution result API gives access

to more information than the dependency insight report.

Signed-off-by: Cedric Champeau <cedric@gradle.com>

Made this change in preparation for deprecating the left shift operator.

+review REVIEW-6236