RFR: 8335257: Refactor code to create Initialized Assertion Predicates into separate class

[Christian Hagedorn]

This is the next patch for Assertion Predicates. It refactors the code to create an Initialized Assertion Predicate. Changes include:

- `clone_assertion_predicate_and_initialize()` currently does two things: Cloning a Template Assertion Predicate and creating an Initailized Assertion Predicate. I've split this method into two methods `clone_template_assertion_predicate()` and `create_initialized_assertion_predicate()`:
  - `clone_template_assertion_predicate()`: Now only clones the template. I have not cleaned the code up further because I will soon replace the `If` node with a dedicated `TemplateAssertionPredicateNode`. 
  - `create_initialized_assertion_predicate()`: I refactored the code for Initialized Assertion Predicate into a separate class `InitializedAssertionPredicate` which creates the complete Initialized Assertion Predicate `If` with a `HaltNode`. I could get rid of some of the arguments because they can be fetched inside the new class methods.
  - Moved `assertion_predicate_has_loop_opaque_node()` asserts to both methods.
- Renamed `AssertionPredicateType::Init_value` -> `AssertionPredicateType::InitValue` (same for last value).

Thanks,
Christian

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Commit messages:
 - 8335257: Refactor code to create Initialized Assertion Predicates into separate class

Changes: https://git.openjdk.org/jdk/pull/19940/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19940&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335257
  Stats: 177 lines in 7 files changed: 125 ins; 26 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/19940.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19940/head:pull/19940

PR: https://git.openjdk.org/jdk/pull/19940