RFR: 8346439: Allow late binding of module services in custom layers [v2]

[David M. Lloyd]

> Custom module layers allow for lazy loading, late binding, and full customization of module dependencies through the `Controller` API. However, it is not possible for custom layer users to late-bind services, which has prevented some popular application containers from moving to use Java modules.
> 
> Add an API to `ModuleLayer.Controller` to allow adding `uses` and `provides` relationships after a module has been defined for custom layers.

David M. Lloyd has updated the pull request incrementally with one additional commit since the last revision:

  Change to an `addProvider` which manages service providers for the layer as whole

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22796/files
  - new: https://git.openjdk.org/jdk/pull/22796/files/d130bb30..1b1bb8da

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22796&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22796&range=00-01

  Stats: 23 lines in 2 files changed: 14 ins; 5 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/22796.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22796/head:pull/22796

PR: https://git.openjdk.org/jdk/pull/22796