Replace configuration module with xcc.Settings

[Mandrenkov]

Context: As part of the migration to the XCC, the configuration module has been replaced by the xcc.Settings class.

Description of the Change:

• Deleted the strawberryfields.configuration module and its corresponding unit tests.
• Added configuration migration notes to the changelog and v0.20.0 migration guide.

Benefits:

• Strawberry Fields has less dead code (the only dependents on the strawberryfields.configuration module were removed by #642 and #645).
• There are clear instructions for migrating Strawberry Fields configurations.

Possible Drawbacks:

• Some features, such as per-project configuration files, are not (yet) supported by the XCC.

Related GitHub Issues: None.

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (integrate-xanadu-cloud-client@da47407). Click here to learn what that means. The diff coverage is n/a.

@@                       Coverage Diff                        @@
##             integrate-xanadu-cloud-client     #649   +/-   ##
================================================================
  Coverage                                 ?   98.27%           
================================================================
  Files                                    ?       73           
  Lines                                    ?     8813           
  Branches                                 ?        0           
================================================================
  Hits                                     ?     8661           
  Misses                                   ?      152           
  Partials                                 ?        0           

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update da47407...4a78c8f. Read the comment docs.