RFR: 8327839: Crash with unboxing and widening primitive conversion in switch

[Aggelos Biboudis]

In cases where the compiler needs to unbox a `long`, `float`, `double` and then run the exactness check, we were getting a crash. While the selector value is always boxed, the type (which controls the execution flow) was not, because the `selectorType` was wrong. This PR addresses this bug.

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Commit messages:
 - 8327839: Crash with unboxing and widening primitive conversion in switch

Changes: https://git.openjdk.org/jdk/pull/18236/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18236&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327839
  Stats: 111 lines in 5 files changed: 99 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/18236.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18236/head:pull/18236

PR: https://git.openjdk.org/jdk/pull/18236