RFR: 8177650: JShell tool: packages in classpath don't appear in completions [v3]

[Jan Lahoda]

> JShell provides the code completion feature, where it suggests possible follow ups for a given snippet prefix. To allow completion for packages, JShell uses a background task to go through known classes and create an index for them.
> 
> There are two problems with this background task:
> - the classpath is read from the JShell's FileManager, but the FileManager may not be configured with the compile options yet, so the classpath may not be filled yet,
> - the module path is not included in the list of paths to paths to search
> 
> This PR proposes to:
> - use FileManager configured by passing the compile options through javac
> - include the module path in the search path

Jan Lahoda has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - Reading module paths directly from the FileManager, to avoid playing with JRT FS.
 - Merge branch 'master' into JDK-8177650
 - Avoiding problems with locked files on Windows.
 - Correcting handling of modular paths.
 - Improving test reliability.
 - 8177650: JShell tool: packages in classpath don't appear in completions

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26137/files
  - new: https://git.openjdk.org/jdk/pull/26137/files/54eed125..b4e0b0f0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26137&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26137&range=01-02

  Stats: 69596 lines in 1762 files changed: 41124 ins; 19092 del; 9380 mod
  Patch: https://git.openjdk.org/jdk/pull/26137.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26137/head:pull/26137

PR: https://git.openjdk.org/jdk/pull/26137