RFR: 8369002: Extract the loop->is_member(get_loop(get_ctrl(node))) pattern in a new function [v3]

[Anton Seoane Ampudia]

> This PR adds a "shorthand" for the common `loop->is_member(get_loop(get_ctrl(node)))` pattern in loop optimizations.
> 
> In PhaseIdealLoop, there is already an `is_member` function that checks if a node is a (nested) member of an IdealLoopTree. In a similar fashion, this changeset adds a `ctrl_is_member` that aims to simplify the common pattern of:
> 
> Node* node_ctrl = get_ctrl(node);
> if (loop->is_member(get_loop(node))) { ... }
> 
> 
> This hopes to provide a bit more readability and code conciseness in such a common operation.
> 
> **Testing:** passes tiers 1-3

Anton Seoane Ampudia has updated the pull request incrementally with one additional commit since the last revision:

  Review comments: nit

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28259/files
  - new: https://git.openjdk.org/jdk/pull/28259/files/8005ac9b..c343e2c5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28259&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28259&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28259.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28259/head:pull/28259

PR: https://git.openjdk.org/jdk/pull/28259