replace dockerfile/dockerignore with patternmatcher/ignorefile

The BuildKit dockerignore package was integrated in the patternmatcher
repository / module. This patch updates our uses of the BuildKit package
with its new location.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

frontend/dockerfile/dockerignore/dockerignore_deprecated.go

@@ -0,0 +1,12 @@
+package dockerignore
+
+import (
+	"io"
+
+	"github.com/moby/patternmatcher/ignorefile"
+)
+
+// ReadAll is an alias for [ignorefile.ReadAll].
+func ReadAll(reader io.Reader) ([]string, error) {
+	return ignorefile.ReadAll(reader)
+}

frontend/dockerfile/dockerignore/dockerignore_test.go

@@ -635,6 +635,7 @@ github.com/moby/locker
 # github.com/moby/patternmatcher v0.6.0
 ## explicit; go 1.19
 github.com/moby/patternmatcher
+github.com/moby/patternmatcher/ignorefile
 # github.com/moby/sys/mount v0.3.3
 ## explicit; go 1.16
 github.com/moby/sys/mount