RFR: 8017234: Hotspot should stop using mapfiles [v5]

[Magnus Ihse Bursie]

> **Summary:** Finally get rid of the mapfiles in Hotspot, and replace it with compiler options and `JNIEXPORT` on all platforms.
> 
> The bug that this PR solves, [JDK-8017234](https://bugs.openjdk.org/browse/JDK-8017234), was created in 2013. Even back then the use of mapfiles in Hotspot was dated, so this is really good riddance with old rubbish.
> 
> This code touches on central but not well understood parts of the Hotspot dynamic library, which has contributed to why this bug has stayed unresolved for so long. I will need to explain this fix in more detail than usually necessary. (Please bare with me if this gets long.) I also anticipate that not all solutions that I've picked will be accepted, and we'll have to discuss how to proceed. I think it is better to have actual concrete code to discuss around, rather than starting by an abstract discussion. To keep this description short, I will post the discussion as a comment to the PR.
> 
> I have run this PR through tier 1-3 in our CI system. I have also carefully checked how the resulting dynamic library differs with this patch (not much; see discussion below). For build system changes, this is often the most relevant metric.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Use #pragma instead of HIDDEN define

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17955/files
  - new: https://git.openjdk.org/jdk/pull/17955/files/ad1d53c9..00e40a7f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17955&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17955&range=03-04

  Stats: 33 lines in 1 file changed: 9 ins; 6 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/17955.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17955/head:pull/17955

PR: https://git.openjdk.org/jdk/pull/17955