RFR: 8307625: Redundant receiver null check in LibraryCallKit::generate_method_call [v3]

[Eric Nothum]

> The null_check_receiver() calls in generate_method_call are redundant as all callers of generate_method_call already perform this check. For future uses of generate_method_call a new assert is introduced that fails if the caller does not null check the receiver.
> Also generally null_check_receiver() should be combined with stopped(), which was not the case here.

Eric Nothum has updated the pull request incrementally with one additional commit since the last revision:

  8307625: adding null_check_receiver() for the uninitialized case, as else only argument(1) is null checked

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14542/files
  - new: https://git.openjdk.org/jdk/pull/14542/files/5763fde8..47c05fd5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14542&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14542&range=01-02

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14542.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14542/head:pull/14542

PR: https://git.openjdk.org/jdk/pull/14542