[code-reflection] Integrated: Use existing code for creating KernelContext_s from its iface buffer schema

[Gary Frost]

Previously we had custom code for creating KernelContext_s C99 code.  

We already had code which could create typedefed structs from iface schemas.

Now KernelContext is an iface mapped buffer we can use this same code.  This stops us from having tto manually ensure that the class and generated C99 code were in sync.

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Commit messages:
 - Use existing code for creating KernelContext_s from its iface buffer schema

Changes: https://git.openjdk.org/babylon/pull/526/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=526&range=00
  Stats: 50 lines in 2 files changed: 10 ins; 21 del; 19 mod
  Patch: https://git.openjdk.org/babylon/pull/526.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/526/head:pull/526

PR: https://git.openjdk.org/babylon/pull/526