[jdk21u-dev] RFR: 8319957: PhaseOutput::code_size is unused and should be removed

[Elif Aslan]

Clean backport.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. There is not any usage.

GHA tested.

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Commit messages:
 - Backport 524aaad98317b1a50453e5a9a44922f481fb3b1e

Changes: https://git.openjdk.org/jdk21u-dev/pull/2459/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2459&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/jdk21u-dev/pull/2459.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2459/head:pull/2459

PR: https://git.openjdk.org/jdk21u-dev/pull/2459