RFR: 8257460: Further CompilerOracle cleanup

[Nils Eliasson]

I got some additional feedback on 8256508: "Improve CompileCommand flag" from Claes.

1. The _type field in TypedMethodMatcher is not used any more. It is derived from the option.

2. The verify_type argument is only used from whitebox API and the check should be pushed out to that code. The check is needed because the option is passed from java as a String and we need to verify that the value type matches the option type.
 
3. The type parameter to TypedMethodMatcher::match isn't used.
 
4. Some code only used for asserts was moved into assert

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Commit messages:
 - Further CompilerOracle cleanup

Changes: https://git.openjdk.java.net/jdk/pull/1528/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1528&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257460
  Stats: 65 lines in 3 files changed: 25 ins; 18 del; 22 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1528.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1528/head:pull/1528

PR: https://git.openjdk.java.net/jdk/pull/1528