[MNG-6881] Inconsistent property semantics against their names in Maven Model Builder

**[Michael Osipov](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=michael-o)** opened **[MNG-6881](https://issues.apache.org/jira/browse/MNG-6881?redirect=false)** and commented

The [model builder](https://maven.apache.org/ref/3.6.3/maven-model-builder/#Model_Interpolation) provides following properties:
* `maven.build.timestamp`, (`build.timestamp`),
* `maven.version` and `maven.build.version`.

From consistency's perspective, I'd either expect `maven.build.timestamp` and `maven.build.version` to contain the timestamp at which Maven was built and and the version of this Maven build.

**But**, it contains the timestamp of the currently built project while the other property still refers to Maven itself.

This is inconsistent. I'd expect everything build related to be in `project.build.*` and with `project.build.timestamp`/`project.build.outputTimestamp`.
* `maven.build.timestamp` along with the format property need to be deprecated and removed; resolved in `project.build.timestamp`/`project.build.timestamp.format`
* `maven.build.version` needs to be deprecated and replaced with something like `maven.banner`/`maven.versionBanner`.

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**Affects:** 3.6.3