Replace the version mode Mainline in 6.x (Part III)

[HHobeck]

Description

Create TrunkBasedVersionStrategy implementation and replace the version mode Mainline in 6.x.

Motivation and Context

For more detail please see the following ADR:

• Replace the version mode Mainline in 6.x #3601

Next steps are:

• Create TrunkBasedVersionStrategy implementation (done)
• Create integration tests for TrunkBasedVersionStrategy (I skip this because of the limit time of reviewer)
• Remove Mainline mode (done)
• Replace VersioningMode with DeploymentMode <<-- Part of this PR
• Add new property with name strategy (type VersionStrategies) to the configuration root level (pending)
• Create documentation for TrunkBased workflow and add breaking changes notes (pending)

How Has This Been Tested?

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[mergify]

Thank you @HHobeck for your contribution!