refactor: Rename `rippled` binary to `xrpld`

[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)
• [X] 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[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 79.1%. Comparing base (62efecb) to head (88ca5a0). :warning: Report is 1 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #5983     +/-   ##
=========================================
- Coverage     79.1%   79.1%   -0.0%     
=========================================
  Files          839     839             
  Lines        71376   71376             
  Branches      8342    8339      -3     
=========================================
- Hits         56436   56433      -3     
- Misses       14940   14943      +3     

see 3 files with indirect coverage changes

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[dangell7]

1. /.rippled in BUILD.md
2. ./rippled in bug_report.md
3. rippled in gitignore
4. rippled --unittest in CONTRIBUTING.md

[bthomee]

1. /.rippled in BUILD.md
2. ./rippled in bug_report.md
3. rippled in gitignore
4. rippled --unittest in CONTRIBUTING.md

Thanks! I went through the .md files and found many more occurrences that could be renamed, and did so. Some occurrences I left as-is (principally github.com/XRPLF/rippled) as the repo won't be renamed until later.

I recently updated the .gitignore file and the binary is no longer listed; only the rippled.cfg but that is being renamed in https://github.com/XRPLF/rippled/pull/6098.