THRIFT-5545: use gradle convention in organizing java project

[Jimexist]

Currently the directory layout of lib/java is:

❯ tree -L 2
.
├── CMakeLists.txt
├── Makefile.am
├── Makefile.in
├── README.md
├── android
│   ├── build.gradle
│   ├── settings.gradle
│   └── src
├── build.gradle
├── code_quality_tools
│   └── findbugs-filter.xml
├── coding_standards.md
├── gradle
│   ├── additionalArtifacts.gradle
│   ├── cloverCoverage.gradle
│   ├── codeQualityChecks.gradle
│   ├── environment.gradle
│   ├── functionalTests.gradle
│   ├── generateTestThrift.gradle
│   ├── publishing.gradle
│   ├── sourceConfiguration.gradle
│   ├── unitTests.gradle
│   └── wrapper
├── gradle.properties
├── gradlew
├── gradlew.bat
├── settings.gradle
├── src
│   └── org
└── test
    ├── org
    └── resources

With a customized gradle config but in fact we can adjust it to the conventional setup:

❯ tree -L 2
.
├── CMakeLists.txt
├── Makefile.am
├── Makefile.in
├── README.md
├── android
│   ├── build.gradle
│   ├── settings.gradle
│   └── src
├── build.gradle
├── code_quality_tools
│   └── findbugs-filter.xml
├── coding_standards.md
├── gradle
│   ├── additionalArtifacts.gradle
│   ├── cloverCoverage.gradle
│   ├── codeQualityChecks.gradle
│   ├── environment.gradle
│   ├── functionalTests.gradle
│   ├── generateTestThrift.gradle
│   ├── publishing.gradle
│   ├── sourceConfiguration.gradle
│   ├── unitTests.gradle
│   └── wrapper
├── gradle.properties
├── gradlew
├── gradlew.bat
├── settings.gradle
└── src
    ├── crossTest
    ├── main
    └── test

i.e. src/{main,test}/{java,resources} so we can remove the customizations.

Official doc https://docs.gradle.org/current/userguide/organizing_gradle_projects.html

• Did you create an Apache Jira ticket? (not required for trivial changes)
• If a ticket exists: Does your pull request title follow the pattern "THRIFT-NNNN: describe my issue"?
• Did you squash your changes to a single commit? (not required, but preferred)
• Did you do your best to avoid breaking changes? If one was needed, did you label the Jira ticket with "Breaking-Change"?
• If your change does not involve any code, include [skip ci] anywhere in the commit message to free up build resources.

[Jimexist]

https://docs.gradle.org/current/userguide/java_library_plugin.html

[ctubbsii]

LGTM

[Jimexist]

had to rebase onto master because of merge conflict