[code-reflection] RFR: [hat] KernelContext from the hat.buffer package renamed to KernelBufferContext

[Juan Fumero]

`KernelContext` from the hat.buffer package renamed to `KernelBufferContext`.

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Commit messages:
 - [hat] KernelContext from the hat.buffer package renamed to KernelBufferContext

Changes: https://git.openjdk.org/babylon/pull/611/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=611&range=00
  Stats: 314 lines in 4 files changed: 146 ins; 147 del; 21 mod
  Patch: https://git.openjdk.org/babylon/pull/611.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/611/head:pull/611

PR: https://git.openjdk.org/babylon/pull/611