RFR: 8312235: [JVMCI] need version of ConstantPool.lookupConstant without eager resolution

[Doug Simon]

The existing `jdk.vm.ci.meta.ConstantPool.lookupConstant(int cpi)` method forces eager resolving of constants. For `DynamicConstant`, `MethodHandle` and `MethodType`, this can mean invoking bootstrap methods, something that should not be done during JIT compilation. To avoid this, this PR adds the following to `jdk.vm.ci.meta.ConstantPool`:

/**
 * Looks up a constant at the specified index.
 *
 * If {@code resolve == false} and the denoted constant is of type
 * {@code JVM_CONSTANT_Dynamic}, {@code JVM_CONSTANT_MethodHandle} or
 * {@code JVM_CONSTANT_MethodType} and it's not yet resolved then
 * {@code null} is returned.
 *
 * @param cpi the constant pool index
 * @return the {@code Constant} or {@code JavaType} instance representing the constant pool
 *         entry
 */
Object lookupConstant(int cpi, boolean resolve);


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Commit messages:
 - update TestDynamicConstant to test new ConstantPool.lookupConstant method
 - add ConstantPool.lookupConstant(int cpi, boolean resolve)

Changes: https://git.openjdk.org/jdk/pull/14927/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14927&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312235
  Stats: 358 lines in 8 files changed: 195 ins; 152 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/14927.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14927/head:pull/14927

PR: https://git.openjdk.org/jdk/pull/14927