[lldb/Plugins] Move member template specialization out of class
This patch should fix the build failure that surfaced when build llvm
with GCC: https://lab.llvm.org/staging/#/builders/16/builds/10450
GCC complained that I explicitely specialized
`ScriptedPythonInterface::ExtractValueFromPythonObject` in a
in non-namespace scope, which is tolerated by Clang.
To solve this issue, the specialization were declared out of the class
and implemented in the source file.
Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>