Update bStats and migrate to new config file

This commit simplifies the Metrics class by using the new base module
from bStats. It also migrates to the new bStats config file that will
be used by plugins that integrate bStats. If a user disabled bStats in
the old config file, this setting will be copied to the new config file.

proxy/build.gradle

@@ -76,6 +76,8 @@ dependencies {
 
     implementation 'com.electronwill.night-config:toml:3.6.3'
 
+    implementation 'org.bstats:bstats-base:2.2.0'
+
     compileOnly 'com.github.spotbugs:spotbugs-annotations:4.1.2'
 
     testImplementation "org.junit.jupiter:junit-jupiter-api:${junitVersion}"
@@ -126,6 +128,8 @@ shadowJar {
     exclude 'it/unimi/dsi/fastutil/objects/*Reference*'
     exclude 'it/unimi/dsi/fastutil/shorts/**'
     exclude 'org/checkerframework/checker/**'
+
+    relocate 'org.bstats', 'com.velocitypowered.proxy.bstats'
 }
 
 artifacts {