RFR: 8255301: Common and strengthen the code in ciMemberName and ciMethodHandle [v2]

[Aleksey Shipilev]

> There is a TODO item in their `get_vm_target`-s. We can clean those up. It looks to me the caller code does not handle `NULL` result well, which means we better `fatal` ourselves before exposing `NULL` to callers and `SEGV`-ing there.

Aleksey Shipilev has updated the pull request incrementally with three additional commits since the last revision:

 - Remove whitespace
 - Simplify the whole thing
 - Simplify, because MemberName::vmtarget already returns Method*

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/825/files
  - new: https://git.openjdk.java.net/jdk/pull/825/files/238bf02a..ec242d22

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=825&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=825&range=00-01

  Stats: 17 lines in 3 files changed: 1 ins; 13 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/825.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/825/head:pull/825

PR: https://git.openjdk.java.net/jdk/pull/825