[code-reflection] RFR: Test for creating a module of functions from invocations

[Paul Sandoz]

Given a set of reflectable methods that form a call graph, we can create a code model that is a module operation containing the functions in that graph where invocation operations are replaced with function call operations.
Starting from the a model of a method, we can traverse it for invocation operations. If the invocation operation's method reference can be resolved to a method and the method has a model then that model is added to the module, the invocation operation is replaced with a function call operation, and it is traversed for invocation operations and so on.

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Commit messages:
 - Test for creating a module of functions from invocations

Changes: https://git.openjdk.org/babylon/pull/81/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=81&range=00
  Stats: 164 lines in 3 files changed: 147 ins; 1 del; 16 mod
  Patch: https://git.openjdk.org/babylon/pull/81.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/81/head:pull/81

PR: https://git.openjdk.org/babylon/pull/81