[jdk17u-dev] RFR: 8301074: Replace NULL with nullptr in share/opto/

[Goetz Lindenmaier]

A lot of hunks were rejected. I replaced all remaining NULL with sed help.
Then I checked for unwanted differences between the original patch and this one.
E.g. in comments the change uses null, but not NULL or nullptr.
I kept NULL in code that is not touched in the original change. 
I do this to simplify later backports, not to clean up the code. 
And code not touched in the original change is subject to a further
change that is not yet backported. Leaving NULL here might simplify
a potential backport here.

There are 3 commits:
1) what could be applied clean.
2) what I changed with sed
3) Cleanups: my manual edits.

-------------

Commit messages:
 - Cleanups
 - Replace remaining by sed
 - Backport 5726d31e56530bbe7dee61ae04b126e20cb3611d

Changes: https://git.openjdk.org/jdk17u-dev/pull/1499/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1499&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301074
  Stats: 5225 lines in 110 files changed: 1 ins; 0 del; 5224 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1499.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1499/head:pull/1499

PR: https://git.openjdk.org/jdk17u-dev/pull/1499