RFR: Minor cleanup and refactoring [v2]

[Ashutosh Mehra]

> Removed unused parameter `aot_code_entry` in `ciEnv::register_method`.
> Removed `preload` local variable in `ciEnv::register_method` as it is always false.
> Refactored `ciEnv::is_compilation_valid` a bit.

Ashutosh Mehra has updated the pull request incrementally with one additional commit since the last revision:

  Rename is_aot_code to is_loading_aot_code
  
  Signed-off-by: Ashutosh Mehra <asmehra at redhat.com>

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Changes:
  - all: https://git.openjdk.org/leyden/pull/101/files
  - new: https://git.openjdk.org/leyden/pull/101/files/a161f27d..ee684780

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=leyden&pr=101&range=01
 - incr: https://webrevs.openjdk.org/?repo=leyden&pr=101&range=00-01

  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/leyden/pull/101.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/101/head:pull/101

PR: https://git.openjdk.org/leyden/pull/101