RFR: 8341784: Refactor TypeVect to use a BasicType instead of a const Type*

[Quan Anh Mai]

Hi,

This patch refactors `TypeVect` to use a `BasicType` instead of a `const Type*` as our current implementation. This conveys the element information in a clearer and safer manner.

Please take a look and leave your reviews,
Thanks a lot.

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Commit messages:
 - more cleanup
 - copyright
 - fix tests
 - cleanup TypeVect

Changes: https://git.openjdk.org/jdk/pull/21414/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21414&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341784
  Stats: 188 lines in 18 files changed: 4 ins; 73 del; 111 mod
  Patch: https://git.openjdk.org/jdk/pull/21414.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21414/head:pull/21414

PR: https://git.openjdk.org/jdk/pull/21414