Build and clean remote builders correctly

Check that the builder and context match what we expect, and if not
remove and re-create them.

lib/kamal/commands/builder/base.rb

@@ -32,7 +32,7 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
       docker(:buildx, :ls)
   end
 
-  def buildx_inspect
+  def inspect_builder
     docker :buildx, :inspect, builder_name unless docker_driver?
   end
 
@@ -101,10 +101,6 @@ class Kamal::Commands::Builder::Base < Kamal::Commands::Base
       config.builder
     end
 
-    def context_host(builder_name)
-      docker :context, :inspect, builder_name, "--format", ENDPOINT_DOCKER_HOST_INSPECT
-    end
-
     def platform_options(arches)
       argumentize "--platform", arches.map { |arch| "linux/#{arch}" }.join(",") if arches.any?
     end