Avoids 0 being used as title ID for all extracted NSPs.

Creates a single KeyManager for the entire container and then passes it into the NCA constructor, eliminating several unnecessary KeyManager reads.

When writing VFS, it initally seemed useful to include a function to in-place convert container files into directories in one homogenous directory structure, but re-evaluating it now there have been plenty of chances to use it and there has always been a better way. Removing as it is unused and likely will not be used.

GetName() returns a std::string by value, not by reference, so after the
std::string_view is constructed, it's not well defined to actually
execute any member functions of std::string_view that attempt to access
the data, as the std::string has already been destroyed. Instead, we can
just use a std::string and erase the last four characters.

If a ticket file was ever a null pointer, we'd cause a null pointer
dereference, as we were calling GetExtension() on the pointer instance.

submission_package: Use std::string's rfind() when looking for the extension in InitializeExeFSAndRomFS()

When searching for a file extension, it's generally preferable to begin
the search at the end of the string rather than the beginning, as the
whole string isn't going to be walked just to check for something at the
end of it.

If an error occurs when constructing the PartitionFilesystem instance,
the constructor would be exited early, which wouldn't initialize the
extracted data member, making it possible for other code to perform an
uninitialized read by calling the public IsExtractedType() member
function. This prevents that.

Like the other two bits of factored out code, this can also be put
within its own function. We can also modify the code so that it accepts
a const reference to a std::vector of files, this way, we can
deduplicate the file retrieval.

Now the constructor for NSP isn't a combination of multiple behaviors in
one spot. It's nice and separate.

This too, is completely separate behavior from what is in the
constructor, so we can move this to its own isolated function to keep
everything self-contained.

This behavior is entirely independent of the surrounding code, so it can
be put in its own function to keep the behavior separate.

We can use early continues here to reduce the amount of nesting.

Orders the elements in the sequence to match the order in which they'll
actually be initialized in.

Now display correct error instead of catch-all MissingProgramNCA