JPERF-941: Annotate signing properties

`PublishTest` was failing with:
```
Some problems were found with the configuration of task ':gatherKeyInformation' (type 'SigningKeyInformationTask').
  - In plugin 'com.atlassian.performance.tools.gradle-release' type 'com.atlassian.performance.tools.SigningKeyInformationTask' property 'signingKeyId' is missing an input or output annotation.

    Reason: A property without annotation isn't considered during up-to-date checking.

    Possible solutions:
      1. Add an input or output annotation.
      2. Mark it as @internal.

    Please refer to https://docs.gradle.org/7.6/userguide/validation_problems.html#missing_annotation for more details about this problem.
  - In plugin 'com.atlassian.performance.tools.gradle-release' type 'com.atlassian.performance.tools.SigningKeyInformationTask' property 'signingPassword' is missing an input or output annotation.

    Reason: A property without annotation isn't considered during up-to-date checking.

    Possible solutions:
      1. Add an input or output annotation.
      2. Mark it as @internal.

    Please refer to https://docs.gradle.org/7.6/userguide/validation_problems.html#missing_annotation for more details about this problem.
  - In plugin 'com.atlassian.performance.tools.gradle-release' type 'com.atlassian.performance.tools.SigningKeyInformationTask' property 'signingSecretKeyRingFile' is missing an input or output annotation.

    Reason: A property without annotation isn't considered during up-to-date checking.

    Possible solutions:
      1. Add an input or output annotation.
      2. Mark it as @internal.

    Please refer to https://docs.gradle.org/7.6/userguide/validation_problems.html#missing_annotation for more details about this problem.
```

src/main/kotlin/com/atlassian/performance/tools/SigningKeyInformationTask.kt

@@ -1,13 +1,19 @@
 package com.atlassian.performance.tools
 
 import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.Input
 import org.gradle.api.tasks.TaskAction
 import org.gradle.kotlin.dsl.extra
 import java.lang.System.getenv
 
 open class SigningKeyInformationTask : DefaultTask() {
+    @Input
     val signingKeyId = "signing.keyId"
+
+    @Input
     val signingSecretKeyRingFile = "signing.secretKeyRingFile"
+
+    @Input
     val signingPassword = "signing.password"
 
     @TaskAction