STD Filesystem VFS

[TomAtkinsonArm]

Description

Replaces OS specific filesystem implementations with std filesystem

This is significantly slower when it comes to enumerating files or folders. Likely due to the conversion between path and string. For now I have added a TODO for future reference

[asuessenbach]

Well, the PR actually LGTM.
I have a few questions/issues on the surroundings, though. Please sorry, if that feels too extensive:

• what's those class Blob and class StdBlob in filesystem.hpp for?
  especially Blob::empty(): can there be the case that size() gives some positive value, but data() is nullptr?
  If some abstraction for a blob is needed, maybe something like using Blob = std::vector<uint8_t>; would be sufficient?
• The argument to the functions folder_exists should be name folder_path
• Why is the blob passed into read_chunk and readFile a std::sharedPtr<Blob> *, not just a Blob *
• Why is FileSystem::readFile virtual? Why does RootFileSystem override it?
• Why are those three enumerate-functions members of RootFileSystem, not FileSystem?
• Most of the functions of FileSystem and RootFileSystem could be const.
• In helpers.cpp, get_file_name: the second argument to substr is the a count, which defaults to npos. That is, as you want to get all the rest right of '/', you can omit it. Any maybe you should add a comment that std::string::npos == -1, so you get the complete string if there's no '/' in path.
• In helpers.cpp, sanitize, maybe the remove trailing / part could be coded like this:

if (!sanitized.empty() && sanitized.back() == '/')
{
    sanitized.pop_back();
}

• In root_file_system.cpp, StdBlob::data() could be implemented as return static_cast<const void *>(buffer.data());
• In root_file_system.cpp, RootFileSystem::enumerate_files(), you should *files = std::move(all_files); if the extension is empty. And you might use helpers::get_file_extension() in the loop there.
• In root_file_system.cpp, mount, maybe like this:

auto it = std::find_if(m_mounts.begin(), m_mounts.end(), [&file_path](auto const & mount){ return mount.first == file_path; });
if ( it != m_mounts.end())
{
    it->second = file_system;
}
else
{
    m_mounts.push_back({file_path, file_system});
}

• In root_file_system.cpp, unmount, maybe like this:

auto it = std::find_if(m_mounts.begin(), m_mounts.end(), [&file_path](auto const & mount){ return mount.first == file_path; });
if ( it != m_mounts.end())
{
    m_mounts.erase(it);
}

• In std_filesystem.cpp, folder_exists and file_exists: do you really want to add file_path to the m_base_path?

[TomAtkinsonArm]

Merging so that #506 may be applied on top