refactor: Rename rippled binary to xrpld and add symlink

[bthomee]

High Level Overview of Change

This change modifies the binary name from rippled to xrpld, and creates a symlink named rippled that points to the xrpld binary.

Context of Change

Per XLS-0095, we are taking steps to rename ripple(d) to xrpl(d).

This change essentially ensures that the binary will now be named xrpld. At the same time, everyone who has automations and other scripts that expect the binary to be named rippled should not be affected, as this change also creates a symlink so rippled redirects to xrpld. The plan is to remove this symlink in about 6 months to give everyone plenty of time to update these automations and scripts to reference xrpld instead.

Note that the previous PR renamed any references to rippled in the CMake files and their contents, but explicitly maintained the rippled binary name by adding an exception. This change now undoes this exception and adds an explicit symlink instead.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.2%. Comparing base (f3a2ec1) to head (57030f0).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #5995     +/-   ##
=========================================
- Coverage     78.2%   78.2%   -0.0%     
=========================================
  Files          816     816             
  Lines        68949   68949             
  Branches      8352    8353      +1     
=========================================
- Hits         53945   53943      -2     
- Misses       15004   15006      +2     

see 3 files with indirect coverage changes

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