RFR: 8314592: Add shortcut to SymbolLookup::find

[Per Minborg]

While `SymbolLookup` correctly uses an `Optional` return to denote whether a symbol has been found by the lookup or not (which enables composition of symbol lookups), many clients end up just calling `Optional::get`, or `Optional::orElseThrow()` on the result.

This PR proposes to add a convenience method `SymbolLookup::findOrThrow` that will do a lookup and, if no symbol can be found, throws an `IllegalArgumentException` with a relevant exception message.

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Commit messages:
 - Remove white space
 - Add SymbolLookup::findOrThrow

Changes: https://git.openjdk.org/jdk/pull/18474/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18474&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314592
  Stats: 93 lines in 21 files changed: 30 ins; 0 del; 63 mod
  Patch: https://git.openjdk.org/jdk/pull/18474.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18474/head:pull/18474

PR: https://git.openjdk.org/jdk/pull/18474