RFR: 8289925 Shared code shouldn't reference the platform specific method frame::interpreter_frame_last_sp()

[Richard Reingruber]

This removes the reference to the platform specific method `frame::interpreter_frame_last_sp()` from the shared method `Continuation::continuation_bottom_sender()`.

The change simply removes the special case for interpreted frames as I cannot see a reason for the distinction between interpreted and compiled frames.

Testing: hotspot_loom and jdk_loom on x86_64 and aarch64.

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Commit messages:
 - Remove platform dependent method interpreter_frame_last_sp() from shared code

Changes: https://git.openjdk.org/jdk/pull/9411/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9411&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289925
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9411.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9411/head:pull/9411

PR: https://git.openjdk.org/jdk/pull/9411