toybox: switch to toybox grep (and egrep/fgrep).

Test: toybox grep tests.
Change-Id: I0061fda14ec1979445cbbdcb41a3e453a8d165de
diff --git a/Android.bp b/Android.bp
index 1293aca..dbcfe23 100644
--- a/Android.bp
+++ b/Android.bp
@@ -289,11 +289,13 @@
                 "dos2unix",
                 "du",
                 "echo",
+                "egrep",
                 "env",
                 "expand",
                 "expr",
                 "fallocate",
                 "false",
+                "fgrep",
                 "file",
                 "find",
                 "flock",
@@ -302,6 +304,7 @@
                 "fsync",
                 "getconf",
                 "getenforce",
+                "grep",
                 "groups",
                 "gunzip",
                 "gzip",