Add Android certificate paths to CURL_CA_PATH

[marcprux]

On Android devices, there is not single aggregate .cer file we can set with CFURLSessionInfoCAINFO, but rather a system managed folder that needs to be specified with CFURLSessionOptionCAPATH. This is similar to how swift-nio handles it (apple/swift-nio-ssl#453).

This is a better solution than #5163, so I'll close that in favor of this.

It only affects Android codepaths, so this change should be low-risk.

[marcprux]

Can I get someone to take a look at this, maybe @compnerd or @parkera?

[compnerd]

Why is try! safe here? Why is the result of .asError being ignored? In particular, it seems that we are losing failure information.

[marcprux]

That's just the convention I observed from every other call to CFURLSesson_easy* functions in this file. They all follow the same pattern.

[compnerd]

I think that we should understand the error handling here, else we can do something like:

do {
  try CFURLSession_easy_setopt_ptr(rawHandle, CFURLSessionOptionCAPATH, UnsafeMutablePointer(mutating: pathPatr)).asError()
} catch let error {
  fatalError(error.message)
}

[marcprux]

This exact pattern is followed 50 other times in this file, and is the documented way to handle errors:

swift-corelibs-foundation/Sources/FoundationNetworking/URLSession/URLSession.swift

Lines 109 to 125 in 8c60d6b

	/// ## Error Handling
	///
	/// Most libcurl functions either return a `CURLcode` or `CURLMcode` which
	/// are represented in Swift as `CFURLSessionEasyCode` and
	/// `CFURLSessionMultiCode` respectively. We turn these functions into throwing
	/// functions by appending `.asError()` onto their calls. This turns the error
	/// code into `Void` but throws the error if it's not `.OK` / zero.
	///
	/// This is combined with `try!` is almost all places, because such an error
	/// indicates a programming error. Hence the pattern used in this code is
	///
	/// ```
	/// try! someFunction().asError()
	/// ```
	///
	/// where `someFunction()` is a function that returns a `CFURLSessionEasyCode`.
	///