RFR: 8319957: PhaseOutput::code_size is unused and should be removed

[Sonia Zaldana Calles]

Hi all, 

This PR removes the unused ```PhaseOutput::code_size / method_size```.

These were moved over from ```src/hotspot/share/opto/compile.hpp``` in the refactor from [8240363](https://bugs.openjdk.org/browse/JDK-8240363). Here's the git link for reference https://github.com/openjdk/jdk/commit/21cd75cb98f658639df14632680e9c5e58f11faa.

I also checked whether there were any usages prior to the refactor and couldn’t find anything so I think it’s safe to remove it. 

Thanks, 
Sonia

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Commit messages:
 - 8319957: PhaseOutput::code_size is unused and should be removed

Changes: https://git.openjdk.org/jdk/pull/18981/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18981&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319957
  Stats: 3 lines in 2 files changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18981.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18981/head:pull/18981

PR: https://git.openjdk.org/jdk/pull/18981