RFR: 8294948: Document IllegalArgumentException and NullPointerException thrown by URLStreamHandler::parseURL and URLStreamHandler::setURL [v9]

[Daniel Fuchs]

> During the review of JDK-8293590, it was noted that some methods in `URLStreamHandler` were missing an `@throws IllegalArgumentException` clause in their API documentation. 
> 
> This change adds the requested information, and also clarifies throwing `MalformedURLException` from URL constructors.
> 
> The CSR can be reviewed here: https://bugs.openjdk.org/browse/JDK-8294984

Daniel Fuchs has updated the pull request incrementally with one additional commit since the last revision:

  More review feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10609/files
  - new: https://git.openjdk.org/jdk/pull/10609/files/f0259f10..5b0692b7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10609&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10609&range=07-08

  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/10609.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10609/head:pull/10609

PR: https://git.openjdk.org/jdk/pull/10609