Add benchmarking tool + improve integer formatting performance

Typical priorities: make it fast before fixing all the bugs. *shrug*

FU/Benchmarks.pod

@@ -0,0 +1,101 @@
+=head1 NAME
+
+FU::Benchmarks - A bunch of automated benchmark results.
+
+=head1 DESCRIPTION
+
+This file is automatically generated from 'bench.pl' in the L<FU> distribution.
+These benchmarks compare performance of some FU functionality against similar
+modules found on CPAN.
+
+=head1 CONTEXT
+
+These benchmarks were performed on 2025-01-28 with perl v5.40.0 on x86_64-linux.
+
+The following module versions were used:
+
+=over
+
+=item L<FU> 0.1
+
+=item L<Cpanel::JSON::XS> 4.38
+
+=item L<JSON::PP> 4.16
+
+=item L<JSON::XS> 4.03
+
+=item L<JSON::SIMD> 1.06
+
+
+
+=back
+
+=head1 BENCHMARKS
+
+=head2 JSON Formatting
+
+These benchmarks run on large-ish arrays with repeated values. JSON encoding is
+sufficiently fast that Perl function calling overhead tends to dominate for
+smaller inputs, but I don't find that overhead very interesting. Other modules
+will likely do better in benchmarks on small inputs.
+
+Also worth noting that JSON::SIMD formatting code is forked from JSON::XS, the
+SIMD parts are only used for parsing.
+
+API object from L<JSON::XS> documentation.
+
+            JSON::PP      5370/s
+    Cpanel::JSON::XS    112211/s
+          JSON::SIMD    128743/s
+            JSON::XS    130606/s
+            FU::Util    130813/s
+
+Small integers
+
+            JSON::PP       113/s
+    Cpanel::JSON::XS      7262/s
+          JSON::SIMD      8217/s
+            JSON::XS      8142/s
+            FU::Util      9154/s
+
+Large integers
+
+            JSON::PP      2136/s
+    Cpanel::JSON::XS     29220/s
+          JSON::SIMD     35834/s
+            JSON::XS     35879/s
+            FU::Util    117838/s
+
+ASCII strings
+
+            JSON::PP      2893/s
+    Cpanel::JSON::XS    118698/s
+          JSON::SIMD    137235/s
+            JSON::XS    135933/s
+            FU::Util    172207/s
+
+Unicode strings
+
+            JSON::PP      5186/s
+    Cpanel::JSON::XS     97154/s
+          JSON::SIMD    109441/s
+            JSON::XS    105691/s
+            FU::Util    106058/s
+
+String escaping (few)
+
+            JSON::PP      4280/s
+    Cpanel::JSON::XS    140105/s
+          JSON::SIMD    161231/s
+            JSON::XS    160077/s
+            FU::Util    182074/s
+
+String escaping (many)
+
+            JSON::PP      2235/s
+    Cpanel::JSON::XS    144829/s
+          JSON::SIMD    161006/s
+            JSON::XS    161246/s
+            FU::Util    136568/s
+
+