Use embedded buildmap in Netkan

[HebaruSan]

Problem

As of #2808, we now load the remote build map every time netkan.exe runs in order to validate that generated metadata matches at least one known game version. This means that per bot pass, we download https://raw.githubusercontent.com/KSP-CKAN/CKAN-meta/master/builds.json 1800 times. This is much more frequent than necessary considering that weeks or months typically pass between KSP versions.

Changes

Now KspBuildMap is rearranged to allow client code to choose the Remote, Cached, or Embedded build map. The default is the same as before: load Cached with Remote and then Embedded as fallbacks if nothing special is done, otherwise load Remote with Cached and then Embedded as fallbacks if Refresh is called. However, now there's also the option to only load the Embedded build map, which is used in the Netkan game version validator. This will reduce network usage by the bot.

Fixes #2809.

[techman83]

I am probably missing something, but where does the build map get embedded for NetKAN?

[HebaruSan]

It's included in the core csproj:

CKAN/Core/CKAN-core.csproj

Lines 151 to 153 in c3ed4b3

	<ItemGroup>
	<EmbeddedResource Include="builds.json" />
	</ItemGroup>

https://github.com/KSP-CKAN/CKAN/blob/master/Core/builds.json

The result is that both ckan.exe and netkan.exe end up with an internal copy of builds.json that is current as of when they were compiled. The downside is that if you use an old executable it may get out of date (hence the preference for the remote build map), but for netkan.exe as used by the bot this is a non-issue because mechanisms to keep netkan.exe up to date are and will be in place.

[techman83]

Ok, that's awesome and the rest LGTM!