RFR: 8299518: HotSpotVirtualMachine shared code across different platforms [v3]

[Yi Yang]

> harmless refactor to share code across different platforms of VirtualMachineImpl:
> 1. Shared code to process command response after requesting a command execution
> 2. Read functionality in SocketInputStream can be reused

Yi Yang has updated the pull request incrementally with one additional commit since the last revision:

  add doc; readImpl/closeImpl to read/close

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11823/files
  - new: https://git.openjdk.org/jdk/pull/11823/files/cb700000..0580ab2d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11823&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11823&range=01-02

  Stats: 15 lines in 5 files changed: 3 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/11823.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11823/head:pull/11823

PR: https://git.openjdk.org/jdk/pull/11823