RFR: 7903704: Expose addresses of native functions [v2]

[Jorn Vernee]

> Add accessors for the address of a native function. This follows the jextract principle of exposing all the information that it has.
> 
> The address is useful in cases where a user needs to pass the address of a native function to be used as a callback by another (higher-order) native function.
> 
> Note: while working on this I noticed that the `TestUtils` file was not being rebuilt when dependent tests were running. Many tests depend on this file to compile generated source code for instance. I've added the needed `@build` tags, and `lib.build` property (the latter only works for the tests under `TestNG.dirs`).

Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:

  Fix test typedef

-------------

Changes:
  - all: https://git.openjdk.org/jextract/pull/228/files
  - new: https://git.openjdk.org/jextract/pull/228/files/c50d8574..2fd79c50

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=228&range=01
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=228&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jextract/pull/228.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/228/head:pull/228

PR: https://git.openjdk.org/jextract/pull/228