Add openrs2 prefix to repo{Username,Password} properties

These might be added to the user's ~/gradle.properties file, at which
point having a per-project prefix is useful.

Ideally I'd have preferred to use openrs2.repo.{username,password}.
However, Gradle properties with dots in them can't be configured with
the ORG_GRADLE_PROJECT_* environment variables, which we use in the
Jenkinsfile.

Jenkinsfile

@@ -6,8 +6,8 @@ pipeline {
             steps {
                 withCredentials([usernamePassword(
                     credentialsId: 'archiva',
-                    usernameVariable: 'ORG_GRADLE_PROJECT_repoUsername',
-                    passwordVariable: 'ORG_GRADLE_PROJECT_repoPassword'
+                    usernameVariable: 'ORG_GRADLE_PROJECT_openrs2RepoUsername',
+                    passwordVariable: 'ORG_GRADLE_PROJECT_openrs2RepoPassword'
                 )]) {
                     withGradle {
                         sh './gradlew --no-daemon clean build publish'

build.gradle.kts

@@ -20,17 +20,17 @@ allprojects {
 
     repositories {
         mavenCentral()
-        if (hasProperty("repoUsername")) {
+        if (hasProperty("openrs2RepoUsername")) {
             maven(url = "https://repo.openrs2.dev/repository/openrs2") {
                 credentials {
-                    username = findProperty("repoUsername")?.toString()
-                    password = findProperty("repoPassword")?.toString()
+                    username = findProperty("openrs2RepoUsername")?.toString()
+                    password = findProperty("openrs2RepoPassword")?.toString()
                 }
             }
             maven(url = "https://repo.openrs2.dev/repository/openrs2-snapshots") {
                 credentials {
-                    username = findProperty("repoUsername")?.toString()
-                    password = findProperty("repoPassword")?.toString()
+                    username = findProperty("openrs2RepoUsername")?.toString()
+                    password = findProperty("openrs2RepoPassword")?.toString()
                 }
             }
         }
@@ -144,8 +144,8 @@ configure(subprojects.filter { it.free }) {
                     }
 
                     credentials {
-                        username = findProperty("repoUsername")?.toString()
-                        password = findProperty("repoPassword")?.toString()
+                        username = findProperty("openrs2RepoUsername")?.toString()
+                        password = findProperty("openrs2RepoPassword")?.toString()
                     }
                 }
             }