RFR: 8361499: Intersection type cast causes javac crash with -Xjcov

[Vicente Romero]

After TransTypes decomposes an intersection type in its components, there is no point keeping the intersection AST around. This could lead to errors in the backend. This PR is proposing lowering the intersection AST to it's first component,

TIA

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Commit messages:
 - 8361499: intersection type cast causes javac crash with -Xjcov

Changes: https://git.openjdk.org/jdk/pull/26203/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26203&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361499
  Stats: 97 lines in 2 files changed: 94 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26203.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26203/head:pull/26203

PR: https://git.openjdk.org/jdk/pull/26203