Fixes the following errors when building with a C++20 toolchain.
I don't really know C++ that well so any pointers would be appreciated.
For the change to the lambda, we can't follow the recommendation to capture `*this` explicitly because that wouldn't compile under C++17. This PR changes the semantics slightly to capture `surface_` by reference, which might be still okay?
For b/289776142
```
error: implicit capture of 'this' with a capture default of '=' is deprecated [-Werror,-Wdeprecated-this-capture]
93 | if (surface_) {
| ^
note: add an explicit capture of 'this' to capture '*this' by reference
91 | raster_thread_merger_->SetMergeUnmergeCallback([=]() {
| ^
| , this
```
```
error: bitwise operation between different enumeration types ('CGImageAlphaInfo' and '(unnamed enum at third_party/apple_sdks/xcode_14_2/iphonesimulator/System/Library/Frameworks/CoreGraphics.framework/Headers/CGImage.h:53:9)') is deprecated [-Werror,-Wdeprecated-anon-enum-enum-conversion]
159 | static_cast<CGBitmapInfo>(kCGImageAlphaPremultipliedLast |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
160 | kCGBitmapByteOrder32Big), // CGBitmapInfo bitmapInfo
| ~~~~~~~~~~~~~~~~~~~~~~~
```
64e17b1a44