RFR: 8332226: "Invalid package name:" from source launcher [v4]

[Christian Stein]

> Please review this change excluding directory paths with invalid elements when computing the packages of a module in source-launch mode.
> 
> Note that this inital iteration of the change only fixes the in-memory computation of package names - the behaviour of the associated module reader implementation is untouched for the time being. This introduces a difference in the set of resources being readable at runtime. For example, see the modified test case: the new and invalid `.bar` directory doesn't show up in the contents of the module - but it is reported by the module reader's `list()` method.
> 
> Note additionally, that above's behaviour is also observed for compiled and exploded modules. Meaning, that with this change being applied, the source mode and compiled mode of the launcher are in line.

Christian Stein has updated the pull request incrementally with two additional commits since the last revision:

 - Drop use of internal module
 - Reapply "Copy `ModulePath`'s exploded directories logic"
   
   This reverts commit 709f4ad3e4bd524d36857e689ec716b30d9024df.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19245/files
  - new: https://git.openjdk.org/jdk/pull/19245/files/709f4ad3..371d505b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19245&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19245&range=02-03

  Stats: 53 lines in 1 file changed: 29 ins; 1 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/19245.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19245/head:pull/19245

PR: https://git.openjdk.org/jdk/pull/19245