RFR: 8333748: javap crash - Fatal error: Unmatched bit position 0x2 for location CLASS [v3]

[Chen Liang]

> Currently, javap crashes for class files that have set non-zero values for undefined access flag bits, as `java.lang.reflect.AccessFlag.maskToAccessFlag` and `java.lang.classfile.AccessFlags.flags` fail. In contrast, the JVMS, though asking for these bits to be set to 0, requires VM to proceed and ignore these bits. javap should emulate the VM behavior and proceed rendering, ignoring these undefined bits.
> 
> In addition, a few bytecode generation utilities in the JDK set unused bits, such as in `java.lang.invoke.MethodHandleImpl.BindCaller#generateInvokerTemplate` and `java.lang.invoke.GenerateJLIClassesHelper#generateCodeBytesForLFs`. Those can be updated in a later cleanup.

Chen Liang has updated the pull request incrementally with two additional commits since the last revision:

 - Improve tests to check unmatched bit position and failure for non-inner-classes
 - Report error for flag problems

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19708/files
  - new: https://git.openjdk.org/jdk/pull/19708/files/84506788..0f3e1a97

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19708&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19708&range=01-02

  Stats: 124 lines in 4 files changed: 55 ins; 34 del; 35 mod
  Patch: https://git.openjdk.org/jdk/pull/19708.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19708/head:pull/19708

PR: https://git.openjdk.org/jdk/pull/19708