Clean up unchecked compile warnings

[izeye]

There are the following warnings:

> Task :micrometer-core:compileTestJava
/Users/user/IdeaProjects/micrometer/micrometer-core/src/test/java/io/micrometer/core/instrument/binder/cache/CaffeineCacheMetricsTest.java:41: warning: [unchecked] unchecked call to CaffeineCacheMetrics(C,String,Iterable<Tag>) as a member of the raw type CaffeineCacheMetrics
    private CaffeineCacheMetrics metrics = new CaffeineCacheMetrics(cache, "testCache", expectedTag);
                                           ^
  where C,K,V are type-variables:
    C extends Cache<K,V> declared in class CaffeineCacheMetrics
    K extends Object declared in class CaffeineCacheMetrics
    V extends Object declared in class CaffeineCacheMetrics
/Users/user/IdeaProjects/micrometer/micrometer-core/src/test/java/io/micrometer/core/instrument/binder/cache/CaffeineCacheMetricsTest.java:77: warning: [unchecked] unchecked call to CaffeineCacheMetrics(C,String,Iterable<Tag>) as a member of the raw type CaffeineCacheMetrics
        CaffeineCacheMetrics metrics = new CaffeineCacheMetrics(cache, "testCache", expectedTag);
                                       ^
  where C,K,V are type-variables:
    C extends Cache<K,V> declared in class CaffeineCacheMetrics
    K extends Object declared in class CaffeineCacheMetrics
    V extends Object declared in class CaffeineCacheMetrics
/Users/user/IdeaProjects/micrometer/micrometer-core/src/test/java/io/micrometer/core/instrument/binder/cache/JCacheMetricsTest.java:70: warning: [unchecked] unchecked call to JCacheMetrics(C,Iterable<Tag>) as a member of the raw type JCacheMetrics
        metrics = new JCacheMetrics(cache, expectedTag);
                  ^
  where C,K,V are type-variables:
    C extends Cache<K,V> declared in class JCacheMetrics
    K extends Object declared in class JCacheMetrics
    V extends Object declared in class JCacheMetrics
/Users/user/IdeaProjects/micrometer/micrometer-core/src/test/java/io/micrometer/core/instrument/binder/cache/JCacheMetricsTest.java:151: warning: [unchecked] unchecked call to JCacheMetrics(C,Iterable<Tag>) as a member of the raw type JCacheMetrics
        metrics = new JCacheMetrics(cache, expectedTag);
                  ^
  where C,K,V are type-variables:
    C extends Cache<K,V> declared in class JCacheMetrics
    K extends Object declared in class JCacheMetrics
    V extends Object declared in class JCacheMetrics
/Users/user/IdeaProjects/micrometer/micrometer-core/src/test/java/io/micrometer/core/instrument/binder/cache/JCacheMetricsTest.java:160: warning: [unchecked] unchecked call to JCacheMetrics(C,Iterable<Tag>) as a member of the raw type JCacheMetrics
        metrics = new JCacheMetrics(cache, expectedTag);
                  ^
  where C,K,V are type-variables:
    C extends Cache<K,V> declared in class JCacheMetrics
    K extends Object declared in class JCacheMetrics
    V extends Object declared in class JCacheMetrics
/Users/user/IdeaProjects/micrometer/micrometer-core/src/test/java/io/micrometer/core/instrument/binder/cache/GuavaCacheMetricsTest.java:46: warning: [unchecked] unchecked call to GuavaCacheMetrics(C,String,Iterable<Tag>) as a member of the raw type GuavaCacheMetrics
    private GuavaCacheMetrics metrics = new GuavaCacheMetrics(cache, "testCache", expectedTag);
                                        ^
  where C,K,V are type-variables:
    C extends Cache<K,V> declared in class GuavaCacheMetrics
    K extends Object declared in class GuavaCacheMetrics
    V extends Object declared in class GuavaCacheMetrics
6 warnings

See gh-2643