RFR: 8365238: 'jfr' feature requires 'services' with 'custom' build variant

[Francesco Andreuzzi]

In this PR I add an `autoconfigure` check to make sure that `jfr` is not built without the feature `services`, which would lead to the following error:

/jdk/src/hotspot/share/jfr/periodic/jfrPeriodic.cpp: In member function ‘virtual void VM_GC_SendObjectCountEvent::doit()’:
/jdk/src/hotspot/share/jfr/periodic/jfrPeriodic.cpp:402:5: error: ‘ObjectCountEventSender’ has not been declared
  402 |     ObjectCountEventSender::enable_requestable_event();
      |     ^~~~~~~~~~~~~~~~~~~~~~
/jdk/src/hotspot/share/jfr/periodic/jfrPeriodic.cpp:404:5: error: ‘ObjectCountEventSender’ has not been declared
  404 |     ObjectCountEventSender::disable_requestable_event();
      |     ^~~~~~~~~~~~~~~~~~~~~~


To reproduce:

sh configure --with-jvm-variants=custom --with-conf-name=cstm --enable-jvm-feature-jfr --enable-jvm-feature-serialgc
make -j hotspot CONF_NAME=cstm

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Commit messages:
 - add check

Changes: https://git.openjdk.org/jdk/pull/26723/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26723&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365238
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26723.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26723/head:pull/26723

PR: https://git.openjdk.org/jdk/pull/26723