tree a09b5e5fba35da5ba6ed521524fdd4546926a310
parent 762da74eeaceba1d77fed0348dad256a4e675f26
author Nan Zhou <nanzhoumails@gmail.com> 1640737545 -0800
committer Nan Zhou <nanzhoumails@gmail.com> 1642633932 -0800

clean up using directives and type alias

Most C++ style guides try to avoid using directives in headers and also
suggest using type alias carefully, according to which, this change does
the following clean up:

1. used Enum class to represent Certificate type
2. removed all using directives: e.g. the phosphor logging namespace;
instead, this change uses using declarations
3. removed unnecessary type alias; in existing codes, we only support
strings as types of UnitToRestart, InstallPath, UploadPath, etc; this
change uses std::string directly
4. moved all alias outside any class scope into source files or an
internal namespace
5. renamed types, constants, classes as per OpenBMC style guide
6. fixed all compilation errors and some warnings after the refactoring;
built with both Clang & GCC

Reference:
https://docs.microsoft.com/en-us/cpp/cpp/header-files-cpp?view=msvc-170#what-to-put-in-a-header-file
https://google.github.io/styleguide/cppguide.html#Namespaces

Tested:
Unit tests

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I58e026934a4e969f4d8877801c8f3c671990468a