Use lines instead of split

```
% cat ~/bench-split.yml
prelude: |
  s = "foo\nbar\nbaz\n"
benchmark:
  '/(?<=\n)/': |
    s.split(/(?<=\n)/)
  '/^/': |
    s.split(/^/)
  'lines': |
    s.lines
Warming up --------------------------------------
           /(?<=\n)/   459.123k i/s -    467.844k times in 1.018994s (2.18μs/i)
                 /^/   467.922k i/s -    469.744k times in 1.003894s (2.14μs/i)
               lines     2.343M i/s -      2.424M times in 1.034677s (426.84ns/i)
Calculating -------------------------------------
           /(?<=\n)/   422.347k i/s -      1.377M times in 3.261232s (2.37μs/i)
                 /^/   477.603k i/s -      1.404M times in 2.939186s (2.09μs/i)
               lines     2.485M i/s -      7.028M times in 2.828757s (402.47ns/i)

Comparison:
               lines:   2484631.6 i/s
                 /^/:    477603.3 i/s - 5.20x  slower
           /(?<=\n)/:    422346.5 i/s - 5.88x  slower
```

1 files changed, 9 insertions, 9 deletions

diff --git a/test/reline/test_config.rb b/test/reline/test_config.rb
index c00c4f8236..1de8ecaf71 100644
--- a/test/reline/test_config.rb
+++ b/test/reline/test_config.rb
@@ -21,7 +21,7 @@ class Reline::Config::Test < Reline::TestCase
   end
 
   def test_read_lines
-    @config.read_lines(<<~LINES.split(/^/))
+    @config.read_lines(<<~LINES.lines)
       set bell-style on
     LINES
 
@@ -71,7 +71,7 @@ class Reline::Config::Test < Reline::TestCase
         set bell-style on
       PARTIAL_LINES
     end
-    @config.read_lines(<<~LINES.split(/^/))
+    @config.read_lines(<<~LINES.lines)
       $include included_partial
     LINES
 
@@ -79,7 +79,7 @@ class Reline::Config::Test < Reline::TestCase
   end
 
   def test_if
-    @config.read_lines(<<~LINES.split(/^/))
+    @config.read_lines(<<~LINES.lines)
       $if Ruby
       set bell-style audible
       $else
@@ -91,7 +91,7 @@ class Reline::Config::Test < Reline::TestCase
   end
 
   def test_if_with_false
-    @config.read_lines(<<~LINES.split(/^/))
+    @config.read_lines(<<~LINES.lines)
       $if Python
       set bell-style audible
       $else
@@ -104,7 +104,7 @@ class Reline::Config::Test < Reline::TestCase
 
   def test_if_with_indent
     %w[Ruby Reline].each do |cond|
-      @config.read_lines(<<~LINES.split(/^/))
+      @config.read_lines(<<~LINES.lines)
         set bell-style none
           $if #{cond}
             set bell-style audible
@@ -119,7 +119,7 @@ class Reline::Config::Test < Reline::TestCase
 
   def test_unclosed_if
     e = assert_raise(Reline::Config::InvalidInputrc) do
-      @config.read_lines(<<~LINES.split(/(?<=\n)/), "INPUTRC")
+      @config.read_lines(<<~LINES.lines, "INPUTRC")
         $if Ruby
       LINES
     end
@@ -128,7 +128,7 @@ class Reline::Config::Test < Reline::TestCase
 
   def test_unmatched_else
     e = assert_raise(Reline::Config::InvalidInputrc) do
-      @config.read_lines(<<~LINES.split(/(?<=\n)/), "INPUTRC")
+      @config.read_lines(<<~LINES.lines, "INPUTRC")
         $else
       LINES
     end
@@ -137,7 +137,7 @@ class Reline::Config::Test < Reline::TestCase
 
   def test_unmatched_endif
     e = assert_raise(Reline::Config::InvalidInputrc) do
-      @config.read_lines(<<~LINES.split(/(?<=\n)/), "INPUTRC")
+      @config.read_lines(<<~LINES.lines, "INPUTRC")
         $endif
       LINES
     end
@@ -146,7 +146,7 @@ class Reline::Config::Test < Reline::TestCase
 
   def test_default_key_bindings
     @config.add_default_key_binding('abcd'.bytes, 'EFGH'.bytes)
-    @config.read_lines(<<~'LINES'.split(/^/))
+    @config.read_lines(<<~'LINES'.lines)
       "abcd": "ABCD"
       "ijkl": "IJKL"
     LINES