RFR: 8257076: os::scan_pages is empty on all platforms

[Sonia Zaldana Calles]

The function os::scan_pages was only ever implemented in Solaris and then removed in [JDK-8244224](https://bugs.openjdk.org/browse/JDK-8244224)

All other platforms have empty implementations and the interface is not optimal as os::scan_pages expects the range to have just one page size, while in reality it can have multiple. 

This PR removes this interface, ensuing empty implementations and all dead code related to page scanning.

Testing: Tier 1.

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

Commit messages:
 - More dead code
 - Removing more dead code
 - 8257076: os::scan_pages is empty on all platforms

Changes: https://git.openjdk.org/jdk/pull/16740/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16740&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8257076
  Stats: 83 lines in 7 files changed: 0 ins; 82 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16740.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16740/head:pull/16740

PR: https://git.openjdk.org/jdk/pull/16740