Previously we were translating "w" to "w", which unlike in C++ doesn't
truncate. See https://issuetracker.google.com/issues/180526528, and for
reference, https://en.cppreference.com/w/cpp/io/c/fopen and
https://en.cppreference.com/w/cpp/io/basic_filebuf/open.
This issue was brought to my attention by the recently published issue
CVE-2023-21036 in the screenshot editing tool on Pixel phones. I'm not
aware of any code in Dolphin that actually uses "w" with an existing
file on Android (when we ask the user for a location to save to using
SAF, a new file is always created), but still, best to fix this.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Any local references get cleaned up when returning to the JVM,
but some of the functions in AndroidCommon return to C++ rather
than the JVM, and functions with loops risk running into the
limit of how many simultaneous local references are allowed.
The Java implementation of getting the list of post-processing
shaders only looked in the Sys folder and not the User folder.
This could be fixed in the Java implementation, but it's
simpler to just call the C++ implementation instead.
The functions with "UTF" in the name use "modified UTF-8" rather
than the standard UTF-8 which Dolphin uses, at least according
to Oracle's documentation, so it is incorrect for us to use them.
This change fixes the problem by converting between UTF-8 and
UTF-16 manually instead of letting JNI do it for us.
Deduplicates code, and gets rid of some problems the old code had
(such as: bad performance when calling native functions, only one
disc showing up for multi-disc games, Wii banners being low-res,
unnecessarily much effort being needed for adding more metadata).
