RFR: 8202750: Reduce the use of get_canonical_path() in CDS

[Calvin Cheung]

Please review this proposed change which includes:

- replace calls to `get_canonical_path()` with `ClassLoader::get_native_path()` which calls `os::native_path()`;
- factor out some code for opening a zip file into `ClassLoader::open_zip_file()`;
- modify `ClassLoader::get_canonical_path()` so that all buffer allocations are within the function.

Testing: Tiers 1 - 4.

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Commit messages:
 - Merge branch 'master' into 8202750-dir-canonical-form
 - replace get_canonical_path() with get_native_path() in ClassLoader::record_result()
 - fix the DirClasspathTest.java test failure on Windows
 - simply the fix
 - 8202750 (initial commit)

Changes: https://git.openjdk.java.net/jdk/pull/2581/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2581&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8202750
  Stats: 60 lines in 2 files changed: 21 ins; 18 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2581.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2581/head:pull/2581

PR: https://git.openjdk.java.net/jdk/pull/2581