Allow multiple manifests to be downloaded from the same depot

[scarletcafe]

Rationale

I want to be able to download multiple versions of a game from a depot, without having to manually do each manifest at a time and without hitting authentication rate limits as brought up in #674.

Problems

There are currently 3 problems that prevent download of multiple manifests from one depot:

Problem 1

Typing -depot 1 -manifest 2 3 produces "Error: -manifest requires one id for every -depot specified"

This is mostly a user experience thing, but if you wanted to e.g. download 4 manifests you would need to do -depot 1 1 1 1 -manifest 2 3 4 5 which is slightly annoying.

This PR fixes this by detecting if exactly one depot ID is specified with multiple manifest IDs, and then uses that depot ID for all manifests (and produces a message so the user knows what's happening).

Problem 2

Typing -depot 1 1 -manifest 2 3 produces "Depot not listed for app 1"

This happens because DepotDownloader tries to validate that all depots requested were retrieved by comparing the length of the retrieved list with the provided list. It deduplicates depots retrieved, so in this case it will compare [1, 1] with [1] and conclude that not all depots were retrieved, failing the download.

This PR fixes it by instead checking that all IDs within depotIdsExpected are contained within depotIdsFound, working even if there are duplicate IDs.

Problem 3

The default output directory does not have subdirectories for manifests, so manifests with the same depot ID will be downloaded to the same place. In addition, specifying your own directory will just download ALL of the contents into the same folder.

This PR fixes it by allowing -dir to have substitution variables %(depot_id), %(depot_version) and %(manifest_id). This means you can do e.g. -depot 1 -manifest 2 3 4 -dir "depots/%(depot_id)/%(manifest_id)" to have it output each manifest into a different directory.

Problem 4

DepotDownloader assumes that either deduplication is not necessary if -dir is not passed, or that it is necessary and will do it across all files if -dir is passed.

This means even if the outputs would go into separate directories due to the string interpolation implemented before, it will still ignore files that have the same name, producing manifest folders with incomplete installs.

This PR fixes it by rewriting the deduplication code to deduplicate only within DepotDownloadInfos that target the exact same output folder. This means deduplication still works in all prior supported cases, but won't prevent the same files being written if they are going to different folders.

This does have the caveat that identical files might be downloaded multiple times, but I'm not sure if there is a good way to detect this before the download has happened, and I think it would add a lot of complexity and need for rewriting. I think the implementation as is works for my use case, and people are free to make a follow-up PR if they think this is important enough.

Caveats

The config for DepotDownloader is usually either placed in the root of depots/ or in the location given by -dir. The config is shared across all of the downloads, so it doesn't belong to any specific depot or manifest ID.

To deal with this, this PR just substitutes all of the variables with 0 for the config directory. This creates an extra, potentially pretty confusing, directory, but it does allow all downloads who use the same -dir format to share a config without issue.

I think this is not an ideal solution but I didn't want to make any unintentional breaking changes so this is the workaround for that.

[FibreTTP]

This seems to fail if -dir isn't passed:

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at DepotDownloader.ContentDownloader.DownloadAppAsync(UInt32 appId, List`1 depotManifestIds, String branch, String os, String arch, String language, Boolean lv, Boolean isUgc) in D:\a\DepotDownloader\DepotDownloader\DepotDownloader\ContentDownloader.cs:line 464
   at DepotDownloader.Program.Main(String[] args) in D:\a\DepotDownloader\DepotDownloader\DepotDownloader\Program.cs:line 324
   at DepotDownloader.Program.<Main>(String[] args)

[scarletcafe]

I've swapped the branch pattern around and it should fix this. From what I can see the other cases of Config.InstallDirectory being null were already correctly checked for so that line was the only one with the oversight.