build: remove deprecations and prep for Gradle 10

[maxlambrecht]

PR Description

This PR removes deprecations reported by ./gradlew build --warning-mode all to keep the build compatible with the upcoming Gradle 10 upgrade.

Changes:

• Replace deprecated dependency “multi-string notation” with single-string coordinates (including classifiers)
• Update protobuf plugin configuration to use explicit platform executables (@exe) and configureEach
• Fix root publishing configuration by applying com.vanniktech.maven.publish only where publishable components exist (apply false at root)
• Upgrade task wiring

[rturner3]

I am seeing a few warnings related to Gradle 10 compatibility when running ./gradlew assemble --warning-mode all with this PR checked out locally:

> Configure project :
Build file '/Users/foo/rturner3/java-spiffe/build.gradle': line 157
Properties should be assigned using the 'propName = value' syntax. Setting a property via the Gradle-generated 'propName value' or 'propName(value)' syntax in Groovy DSL has been deprecated. This is scheduled to be removed in Gradle 10. Use assignment ('jacocoReportPath = <value>') instead. Consult the upgrading guide for further information: https://docs.gradle.org/9.2.1/userguide/upgrading_version_8.html#groovy_space_assignment_syntax
        at build_e1srl9z1oegpqg7hzi4ngr85x$_run_closure5.doCall$original(/Users/foo/rturner3/java-spiffe/build.gradle:157)
        (Run with --stacktrace to get the full stack trace of this deprecation warning.)
        at build_e1srl9z1oegpqg7hzi4ngr85x.run(/Users/foo/rturner3/java-spiffe/build.gradle:156)
        (Run with --stacktrace to get the full stack trace of this deprecation warning.)

> Configure project :java-spiffe-core
Declaring dependencies using multi-string notation has been deprecated. This will fail with an error in Gradle 10. Please use single-string notation instead: "com.google.protobuf:protoc:3.25.5:osx-aarch_64@exe". Consult the upgrading guide for further information: https://docs.gradle.org/9.2.1/userguide/upgrading_version_9.html#dependency_multi_string_notation
Declaring dependencies using multi-string notation has been deprecated. This will fail with an error in Gradle 10. Please use single-string notation instead: "io.grpc:protoc-gen-grpc-java:1.77.0:osx-aarch_64@exe". Consult the upgrading guide for further information: https://docs.gradle.org/9.2.1/userguide/upgrading_version_9.html#dependency_multi_string_notation

I believe that the first warning will be addressed once #382 is merged. Is the intention to handle the remaining warnings in this PR or will they be addressed in a later PR?

[maxlambrecht]

I am seeing a few warnings related to Gradle 10 compatibility when running ./gradlew assemble --warning-mode all with this PR checked out locally:

> Configure project :
Build file '/Users/foo/rturner3/java-spiffe/build.gradle': line 157
Properties should be assigned using the 'propName = value' syntax. Setting a property via the Gradle-generated 'propName value' or 'propName(value)' syntax in Groovy DSL has been deprecated. This is scheduled to be removed in Gradle 10. Use assignment ('jacocoReportPath = <value>') instead. Consult the upgrading guide for further information: https://docs.gradle.org/9.2.1/userguide/upgrading_version_8.html#groovy_space_assignment_syntax
        at build_e1srl9z1oegpqg7hzi4ngr85x$_run_closure5.doCall$original(/Users/foo/rturner3/java-spiffe/build.gradle:157)
        (Run with --stacktrace to get the full stack trace of this deprecation warning.)
        at build_e1srl9z1oegpqg7hzi4ngr85x.run(/Users/foo/rturner3/java-spiffe/build.gradle:156)
        (Run with --stacktrace to get the full stack trace of this deprecation warning.)

> Configure project :java-spiffe-core
Declaring dependencies using multi-string notation has been deprecated. This will fail with an error in Gradle 10. Please use single-string notation instead: "com.google.protobuf:protoc:3.25.5:osx-aarch_64@exe". Consult the upgrading guide for further information: https://docs.gradle.org/9.2.1/userguide/upgrading_version_9.html#dependency_multi_string_notation
Declaring dependencies using multi-string notation has been deprecated. This will fail with an error in Gradle 10. Please use single-string notation instead: "io.grpc:protoc-gen-grpc-java:1.77.0:osx-aarch_64@exe". Consult the upgrading guide for further information: https://docs.gradle.org/9.2.1/userguide/upgrading_version_9.html#dependency_multi_string_notation

I believe that the first warning will be addressed once #382 is merged. Is the intention to handle the remaining warnings in this PR or will they be addressed in a later PR?

The first warning went away after merging #382.

Regarding the other 2 warnings, I initially could not find a fix for it, since changing the artifact = "group:module:version:classifier@exe" strings does not eliminate the warning. After further investigation, I addressed it by avoiding the plugin’s internal dependency creation altogether and wiring the tools via explicit configurations and path = ..., which removes the deprecated API usage and makes the build compatible with Gradle 10.