Custom CSL Styles & build-time loading

Follow-up to #12472

A. Functionality

• The list of available CSL styles is now determined at build-time.
  Common metadata (path, title, isNumericStyle) from internal .csl files is pre-fetched and stored in a JSON file (citation-style-catalog.json) via CitationStyleCatalogGenerator. This reduces delays in population of the styles list (and cuts off some parsing overhead) for both the OO/LO integration as well as the preview viewer.

  Form:

{
  "path" : "academy-of-management-review.csl",
  "isNumeric" : false,
  "title" : "Academy of Management Review"
},

• Revamped Select Style dialog UI - now both the CSL and JStyle tabs uniformly use TableView.

• Support for external CSL styles:

  

B. Code quality

• Separation of concerns - CitationStyle now only handles modelling of a CSL style. CitationStyleCatalogGenerator along with CSLStyleLoader takes care of loading/removal of styles. CSLStyleUtils handles creation of CSL style instances and parsing.
• Lot of refactoring & modularization of code (e.g. in StyleSelectDialogView, the handling of different components is now much more neatly compartmentalized for both CSL styles and JStyles. StyleSelectDialogViewModel has also been refactored for better manageability).
• Complete renaming of OOBibStyle to JStyle.
• Removal of unified style handling components from the JStyle class.

Closes #12337

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (if change is visible to the user)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.