Re-structuring and renaming of contracts code.

[jplodge-pro]

NOTE: This PR is #66 ff-merged to give a cleaner change profile.

Reason

This is a quick change to address some of the issues I have with the contracts codebase, like:

1. Naming, for example:
   • CredbullBaseVault the root of the Vault contract hierarchy.
     • Prefixed with Credbull, but not actually deployed (the only other 'Credbull' prefixed contracts are those that are deployed).
     • Base, but is that really necessary? Also, in that vein, it could be BaseMaturityVault.
   • We have MockToken and MockStableCoin in test, but also CredbullBaseVaultMock (same for all vaults).
2. Inconsistent naming (contracts, structs, files), for example:
   • whitelist and kyc used interchangeably.
   • For WindowPlugIn is it a mature window, or a redemption window? Seeing as the other window is the deposit window, it seems to me that it should be redemption. But it's IS mature and is referenced interchangeably as 'mature' and 'redemption'.
3. Uncategorised (as far as I can tell) directory structure. For example:
   • base, vaults AND extensions fulfilling essentially the same purpose.
   • interface containing cross-functional interfaces.
     • IErrors has been deleted
   • Root (src) containing deployable contracts AND factories

Adopted Changes

• Categorised singular sub-directories, like vault and factory.
  • 
  • 
• All deployable contracts are in the root of the src directory.
  • 
• All things PlugIn are now re-named Plugin.
• All Vault/Plugin Contracts have a XParams struct capturing their construction values.
  • NOTE: When an XParams contains a reference to another XParams, the member name is x.
    • 
  • This will lead to a usage pattern like this: params.maturityVault.vault.custodian;, where params is a FixedYieldVaultParams. Thus the purpose is clear due to the call chain off params and no need to have an xParams at every level of the tree.
• All Vault Contract constructors accept an instance of their parameters struct.
• Changed the matureWindow in WindowPlugIn to redemptionWindow.
  • As per the discussion on #engineering:
    • WindowPlugin relates to deposit/redemption windows.
    • MaturityVault is a Vault that 'pushes' the assets to the depositing accounts on maturation. BUT it should not know anything of promisedYield or fixedYield as those are FixedYieldVault concerns.
      • Moved _fixedYield to FixedYieldVault.
      • Modified expectedAssetsOnMaturity to be virtual and to have a simple implementation.
• All test support contracts are now called SimpleX.
  • As @lucasia pointed out, 'Mock' was over-used, and most instances were not actually 'mock's.
  • This change may have gone a bit too far. Opinions, please!
• All testing source is in .t.sol files. We had .m.sol and .sol files in test.
• Added utility import shortcuts to remappings.txt
  • So we can import from "@credbull/..." for src, "@script/..." for script code and "@test/..." for `test code.
  • Usage of this is ONLY INTENDED FOR test and script source (where the '../../..' imports are prevalent).

Extent

• The PR (Updates to all components enforced by restructuring of contracts. #72) for all knock-on effects has been merged into this PR.

[openzeppelin-code]

Re-structuring and renaming of contracts code.

Generated at commit: 41cf88be923bb52854892fd231c52717c2609a14

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	1 0 0 4 14 19
Dependencies	Critical High Medium Low Note Total	0 0 0 0 0 0

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For more details view the full report in OpenZeppelin Code Inspector