Fix potential exception and resource leak

[xelement]

Issue

1. If we want to determine memory allocation result，we should use 'new(std::nothrow)' instead of new，because 'new' failed will throw 'std::bad_alloc' exception. It may cause potential exception since modified code path does not have any try catch.

2. The original code can cause resource leak if just return 'MFX_ERR_MEMORY_ALLOC', see libvpl/src/mfx_dispatcher_vpl_loader.cpp:line 211，276

Solution

1. Use 'new(std::nothrow)' instead of 'new'
2. Free resouce before return 'MFX_ERR_MEMORY_ALLOC'

How Tested

1. libvpl/src/mfx_dispatcher_vpl_loader.cpp:line 211，276
   1.1 set *'LibInfo libInfo = nullptr' (If no memory，new (std::nothrow) will return nullptr)
   1.2 run vpl-timing with argument '-e' ( run 'MFXEnumImplementations ' function)
   1.3 MFXEnumImplementations return 'MFX_ERR_NOT_FOUND'，No memory leak，No crash，it was what we desired

2. libvpl/src/mfx_dispatcher_vpl_loader.cpp:line 999
   2.1 set *'ImplInfo implInfo = nullptr'
   2.2 run vpl-timing
   2.3 MFXCreateSession return 'MFX_ERR_NOT_FOUND'，No memory leak，No crash，it was what we desired

3. libvpl/src/mfx_dispatcher_vpl_loader.cpp:line 1135
   Same as 2

4. libvpl/src/mfx_dispatcher_vpl_lowlatency.cpp:line 80
   4.1 set 'libInfo = nullptr'
   4.2 run vpl-timing with argument '-f'
   4.3 MFXCreateSession return 'MFX_ERR_NOT_FOUND'，No memory leak，No crash，it was what we desired