Document the Gradle build configuration

[nathanklick]

Description

The Gradle build logic needs to be documented including:

• The build-logic folder
• Project/module naming standards
• Use of the GradleX tooling
• Available custom tasks

[jjohannes]

As part of this (or split-out into separate issue): Use unified naming and structure in all repositories

• https://github.com/hashgraph/hedera-services
• https://github.com/hashgraph/pbj
• https://github.com/hashgraph/hedera-sdk-java
• ...

For example:

• Use gradle/plugins as "build logic" folder everywhere
• Use com.hedera.gradlebuild... as namespace for all convention plugin
• Use similar naming for plugins that do similar things in the different repos
• Use the exact same names for convention plugins that do exactly the same in different repos (later we could think about sharing the logic between repos)

[jjohannes]

Start with the user documentation

As part of this, move the following to docs folder in root, update where appropriate. Make sure we have a full "how and what to use Gradle for in daily development" guide.

• branch-naming-conventions
• docker-quickstart <-- this is services specific, generally no docker is needed for development
• gradle-quickstart
• hedera-java-style-guide
• intellij-quickstart
• maintainers-guide

[jjohannes]

I plan to document the Gradle setup itself in the README of the new repository we'll create for the Gradle setup as part of #14255