faster SRCINFO parsing + memory-based building

Switched to parsing srcinfo with channels on all available cpus, speeding
up srcinfo-parsing and queue generation by a lot.

New memory-limit based building will max out the available memory while
not building the same packages at the same time for different marchs,
fixing some long-standing bugs like firefox not building at the same time
because the same ports are used for profile-based optimization. This
also drops the artificial delay on build-start, speeding up things even
more. This also means there is no hard-coded limit on how many packages
can be build at once anymore. As long as there is RAM available, builds will be
started.

ent/schema/dbpackage.go

@@ -15,7 +15,8 @@ func (DbPackage) Fields() []ent.Field {
 	return []ent.Field{
 		field.String("pkgbase").NotEmpty().Immutable(),
 		field.Strings("packages").Optional(),
-		field.Enum("status").Values("skipped", "failed", "build", "queued", "delayed", "building", "latest", "signing", "unknown").Default("unknown").Optional(),
+		field.Enum("status").Values("skipped", "failed", "build", "queued", "delayed", "building",
+			"latest", "signing", "unknown").Default("unknown").Optional(),
 		field.String("skip_reason").Optional(),
 		field.Enum("repository").Values("extra", "core", "community"),
 		field.String("march").NotEmpty().Immutable(),