This provides a significant speedup for symbol, true, false,
nil, and 0-9, class/module, and a small speedup in most other cases.

Speedups (using included benchmarks):
:symbol        :: 60%
0-9            :: 50%
Class/Module   :: 50%
nil/true/false :: 20%
integer        :: 10%
[]             :: 10%
""             :: 3%

One reason this approach is faster is it reduces the number of
VM instructions for each interpolated value.

Initial idea, approach, and benchmarks from Eric Wong. I applied
the same approach against the master branch, updating it to handle
the significant internal changes since this was first proposed 4
years ago (such as CALL_INFO/CALL_CACHE -> CALL_DATA). I also
expanded it to optimize true/false/nil/0-9/class/module, and added
handling of missing methods, refined methods, and RUBY_DEBUG.

This renames the tostring insn to anytostring, and adds an
objtostring insn that implements the optimization. This requires
making a few functions non-static, and adding some non-static
functions.

This disables 4 YJIT tests.  Those tests should be reenabled after
YJIT optimizes the new objtostring insn.

Implements [Feature #13715]

Co-authored-by: Eric Wong <e@80x24.org>
Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>
Co-authored-by: Yusuke Endoh <mame@ruby-lang.org>
Co-authored-by: Koichi Sasada <ko1@atdot.net>

Pass in ec to vm_opt_newarray_{max,min}. Avoids having to
call GET_EC inside the functions, for better performance.

While here, add a test for Array#min/max being redefined to
test_optimization.rb.

Fixes [Bug #18180]

These were introduced in the test for tracing optimized methods
added in 48c8df9e0eb295af06d593ce37ce1933c0ee1d90.

This updates the trace instructions to directly dispatch to
opt_send_without_block.  So this should cause no slowdown in
non-trace mode.

To enable the tracing of the optimized methods, RUBY_EVENT_C_CALL
and RUBY_EVENT_C_RETURN are added as events to the specialized
instructions.

Fixes [Bug #14870]

Co-authored-by: Takashi Kokubun <takashikkbn@gmail.com>

because the name "MJIT" is an internal code name, it's inconsistent with
--jit while they are related to each other, and I want to discourage future
JIT implementation-specific (e.g. MJIT-specific) APIs by this rename.

[Feature #17490]

* Otherwise those tests, etc cannot run on alternative Ruby implementations.

CI fails with GC while `foo{}`, so that disable GC for this script.

instead of :TOTAL of ObjectSpace.count_objects.

This test had failed very occasionally:

https://rubyci.org/logs/rubyci.s3.amazonaws.com/centos8/ruby-master/log/20200521T033004Z.fail.html.gz
```
  1) Failure:
TestRubyOptimization#test_block_parameter_should_not_create_objects [/home/chkbuild/chkbuild/tmp/build/20200521T033004Z/ruby/test/ruby/test_optimization.rb:713]:
<0> expected but was
<407>.
```

This test of lazy proc creation checks if no object is created during a
method call.  However, calling a method itself increases the count of
objects because method cache is now an object (T_MEMO).
The reason why this test rarely fails is because the test was buggy; it
checked the count of :TOTAL, but :TOTAL count changes only when the GC
heap is expanded.  Creating one object rarely causes heap expansion.
The test must have checked not only :TOTAL but also the count of :FREE.

Instead, this change more directly checks :T_DATA.  Note that a Proc
object is T_DATA.