Update antlr dependency from 4.5.3 to 4.7.1 switch to gradle in idl2k

This is a squashed and rebased commit of https://github.com/JetBrains/kotlin/pull/1945

- add idl2k to default gradle build lifecycle
- removemaven build completely
- invert maven's `idl2k.deploy.skip` to `idl2k.deply` in gradle
(false by default)
- antlr upgrade from 4.5.3 to 4.7.1 - I'd have to slightly modify WebIDL.g4 definition though -
and updated copyright accordingly - my updates were based on
https://raw.githubusercontent.com/antlr/grammars-v4/master/webidl/WebIDL.g4
- I've checked all generated output to make sure it is identical to
what we hade before dependency update.
- Package idl2k according to our souce code guidelines

settings.gradle

@@ -196,7 +196,8 @@ include ":kotlin-build-common",
         ":kotlinx-serialization-compiler-plugin",
         ":kotlinx-serialization-ide-plugin",
         ":kotlin-serialization",
-        ":kotlin-serialization-unshaded"
+        ":kotlin-serialization-unshaded",
+        ":kotlin-idl2k"
 
 def isTeamcityBuild = hasProperty("teamcity") || System.getenv("TEAMCITY_VERSION") != null
 def includeUltimate = hasProperty("intellijUltimateEnabled") && intellijUltimateEnabled != 'false'
@@ -317,3 +318,4 @@ project(':kotlinx-serialization-compiler-plugin').projectDir = file("$rootDir/pl
 project(':kotlinx-serialization-ide-plugin').projectDir = file("$rootDir/plugins/kotlin-serialization/kotlin-serialization-ide")
 project(':kotlin-serialization').projectDir = file("$rootDir/libraries/tools/kotlin-serialization")
 project(':kotlin-serialization-unshaded').projectDir = file("$rootDir/libraries/tools/kotlin-serialization-unshaded")
+project(':kotlin-idl2k').projectDir = file("$rootDir/libraries/tools/idl2k")