Ignore dependency self conflicts

[HebaruSan]

Problem

• On a completely fresh install, AstronomersVisualPack shows as compatible
• If you install Scatterer, AstronomersVisualPack (which depends on Scatterer) shows as incompatible

That doesn't make sense. Installing a dependency shouldn't ever mark the depending module as incompatible.

Cause

• AstronomersVisualPack depends on Scatterer
• Scatterer conflicts with itself (see Add self-conflict to Scatterer NetKAN#4541 and Cannot install Scatterer #1870)

Scatterer's self-conflict relationship trips this check:

CKAN/Core/Registry/AvailableModule.cs

Lines 123 to 133 in 2119b58

	if (module.conflicts != null)
	{
	foreach (RelationshipDescriptor rel in module.conflicts)
	{
	// If any of the conflicts are present, fail
	if (rel.MatchesAny(others, null, null))
	{
	return false;
	}
	}
	}

... but only when it's installed, via this block:

CKAN/Core/Registry/AvailableModule.cs

Lines 99 to 102 in 2119b58

	if (installed != null)
	{
	modules = modules.Where(m => DependsAndConflictsOK(m, installed));
	}

... passed from here:

CKAN/Core/Registry/Registry.cs

Lines 708 to 713 in 2119b58

	.Select(am => am.Latest(
	ksp_version,
	relationship_descriptor,
	InstalledModules.Select(im => im.Module),
	toInstall
	))

... while checking dependencies for compatibility here:

CKAN/Core/Registry/Registry.cs

Lines 537 to 541 in 2119b58

	if (!dependency.MatchesAny(null, InstalledDlls.ToHashSet(), InstalledDlc)
	&& !dependency.LatestAvailableWithProvides(this, ksp_version).Any())
	{
	return false;
	}

Changes

Now when checking that conflicts are OK for an available module, we filter any copies of itself (i.e., with matching identifier) out of the list of potential conflicting modules. This prevents the Scatterer self conflict from breaking modules that depend on Scatterer.

We could try ignoring the self conflict relationships instead, but that would miss other modules that provide the conflicting identifier, which presumably would be part of why such conflicts would be set up in the first place.

Fixes #2719 (the part of it that can't be explained as expected behavior).