RFR: 8202750: Reduce the use of get_canonical_path() in CDS [v2]

[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.

Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:

  per review comments from @iklam

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2581/files
  - new: https://git.openjdk.java.net/jdk/pull/2581/files/dc755372..bf940008

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2581&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2581&range=00-01

  Stats: 38 lines in 3 files changed: 17 ins; 14 del; 7 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