Remove Guava cache support

This commit removes `GuavaCache` and support classes. Caffeine supersedes
the caching support in the Google Guava library with an actively maintained
Java 8+ version in standalone form.

As it is the only Guava feature Spring framework integrates with, this
commit removes effectively any reference to Guava.

Issue: SPR-13797

Author: snicoll

build.gradle

@@ -43,7 +43,6 @@ configure(allprojects) { project ->
 	ext.freemarkerVersion    = "2.3.23"
 	ext.groovyVersion        = "2.4.7"
 	ext.gsonVersion          = "2.7"
-	ext.guavaVersion         = "19.0"
 	ext.hamcrestVersion      = "1.3"
 	ext.hibernate5Version    = "5.2.1.Final"
 	ext.hibval5Version       = "5.2.4.Final"
@@ -612,7 +611,6 @@ project("spring-context-support") {
 		optional(project(":spring-tx"))  // for Quartz support
 		optional("javax.mail:javax.mail-api:${javamailVersion}")
 		optional("javax.cache:cache-api:1.0.0")
-		optional("com.google.guava:guava:${guavaVersion}")
 		optional("com.github.ben-manes.caffeine:caffeine:${caffeineVersion}")
 		optional("net.sf.ehcache:ehcache:${ehcacheVersion}")
 		optional("org.quartz-scheduler:quartz:2.2.3")