RFR: 8296433: Encountered null CLD while loading shared lambda proxy class

[Calvin Cheung]

Please review this simple fix for calling `load_shared_class()`, which initializes `class_loader_data` prior to `set_nest_host()` in `SystemDictionary::load_shared_lambda_proxy_class()`.  Otherwise, a null `class_loader_data` would be encountered in `set_nest_host()`; it would fail the added assertion in `set_nest_host()`.

Passed tiers 1 and 2 testing on Oracle supported platforms.

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Commit messages:
 - 8296433: Encountered null CLD while loading shared lambda proxy class

Changes: https://git.openjdk.org/jdk/pull/11031/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11031&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296433
  Stats: 13 lines in 2 files changed: 7 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11031.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11031/head:pull/11031

PR: https://git.openjdk.org/jdk/pull/11031