RFR: 8314592: Add shortcut to SymbolLookup::find [v6]

[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.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Change exception type

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18474/files
  - new: https://git.openjdk.org/jdk/pull/18474/files/2ebac9fc..e2f6c4c9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18474&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18474&range=04-05

  Stats: 4 lines in 1 file changed: 1 ins; 0 del; 3 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