Moves the construction of CompilationInfo for unoptimized code into
GenerateUnoptimizedCode in preparation for making it owned by the
unoptimized compilation jobs (to be done in a followup CL).

This CL also adds a new constructor for creation of unoptimized
CompilationInfos with fields correctly initialized and updates the existing
constructor to he exclusively for optimized compilation. Finally, also moves
the call to RecordFunctionCompilation with LAZY_COMPILE_TAG recording into
FinalizeUnoptimizedCompilationJob where it is called for other unoptimized
compiles.

BUG=v8:5203,v8:6659

Change-Id: Icfd7f56588073f2fc547e002db9fa99843ed2e8b
Reviewed-on: https://chromium-review.googlesource.com/598908
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47160}