feat: use OS conform path for storing cached results

Instead of storing cached values in the config yaml, they are now stored
under these OS specific locations:
* Linux: `~/.cache/k8sgpt`
* MacOS: `~/Library/Caches`
* Windows: `%LocalAppData%\cache`

Additionally a `Cache` package and interface has been introduced.
Currently there are two implementations:
* Noop - Doesn't do anything
* FileBased - Stores data in files under the locations listed above

fixes #323

Signed-off-by: Patrick Pichler <git@patrickpichler.dev>

pkg/cache/cache.go

@@ -0,0 +1,15 @@
+package cache
+
+type ICache interface {
+	Store(key string, data string) error
+	Load(key string) (string, error)
+	Exists(key string) bool
+}
+
+func New(noCache bool) ICache {
+	if noCache {
+		return &NoopCache{}
+	}
+
+	return &FileBasedCache{}
+}