[deoptimizer] Begin splitting classes into files

This CL keep the Deoptimizer class in deoptimizer.{h,cc} and moves
everything else into translations.{h,cc}. Translations may be further
split up in follow-up work.

Drive-by: Remove dead code and clean up includes.

Bug: v8:11332
Change-Id: If774399843da1322c01e03d71c97b10fc88e45cb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2639955Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72228}

BUILD.gn

@@ -2635,6 +2635,8 @@ v8_source_set("v8_base_without_compiler") {
     "src/deoptimizer/deoptimize-reason.h",
     "src/deoptimizer/deoptimizer.cc",
     "src/deoptimizer/deoptimizer.h",
+    "src/deoptimizer/translations.cc",
+    "src/deoptimizer/translations.h",
     "src/diagnostics/basic-block-profiler.cc",
     "src/diagnostics/basic-block-profiler.h",
     "src/diagnostics/code-tracer.h",