Allow configuring cache folder (#2357)

* Set all clients to dev_download for make get-music

* Use multiple TranscodingCache instances in tests

This fixes flaky tests. The issue is that the TranscodingCache object
was being reused in tests from media_stream_Internal_test.go and
media_stream_test.go. If tests from the former was run first, the cache
would be filled up, so that when running tests from the latter, the `NON
seekable` test would fail.

* Allow configuring cache folder

This commit introduces a new configuration option to configure the cache
folder. This allows the cache to be in a separate folder such as
/var/cache/navidrome on Linux distributions.

* Fix tests

* Removed unused test setup code

---------

Co-authored-by: Deluan <deluan@deluan.com>
Co-authored-by: Deluan <deluan@navidrome.org>

tests/init_tests.go

@@ -23,7 +23,7 @@ func Init(t *testing.T, skipOnShort bool) {
 		confPath, _ := filepath.Abs(filepath.Join(appPath, "tests", "navidrome-test.toml"))
 		println("Loading test configuration file from " + confPath)
 		_ = os.Chdir(appPath)
-		conf.LoadFromFile("tests/navidrome-test.toml")
+		conf.LoadFromFile(confPath)
 
 		noLog := os.Getenv("NOLOG")
 		if noLog != "" {