Config: Add more utest for env config. v6.0.147 v7.0.4 (#4142)

1. don't use static variable to store the result;
2. add more UT to handle the multi value and values with whitespaces;

related to #4092 


16e569d823/trunk/src/app/srs_app_config.cpp (L71-L82)

`static SrsConfDirective* dir` removed, this static var here is to avoid
the memory leak, I add the `SrsConfDirective` instance to the `env_dirs`
directive container, which will destroy itself inside `SrsConfig`
destructor.

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Co-authored-by: winlin <winlinvip@gmail.com>

trunk/src/core/srs_core_version6.hpp

@@ -9,6 +9,6 @@
 
 #define VERSION_MAJOR       6
 #define VERSION_MINOR       0
-#define VERSION_REVISION    146
+#define VERSION_REVISION    147
 
 #endif

trunk/src/core/srs_core_version7.hpp

@@ -9,6 +9,6 @@
 
 #define VERSION_MAJOR       7
 #define VERSION_MINOR       0
-#define VERSION_REVISION    3
+#define VERSION_REVISION    4
 
 #endif