Change package name & replace custom functions

[RayStick]

So many files have changed because the package has changed from browseMetadata to mapmetadata to

1. Be more in line with naming best practice
2. mappping (not browsing) is a better representation of the contribution this package brings

Other changes include:

• combined the browse function into the map function to simplify package use for the user
• changed some function names to match object_verb convention
• moving from json to csv as the the metadata input to reflect the new structure from HDRUK Gateway
• remove some custom functions, because utils already offered these! (or very similar)
• update unit tests to match the new code structure
• update package dependencies to match the new code structure
• update documentation to match the new code structure and the new naming

Checklist for the author of this PR:

• [if package files were edited] I have run these checks locally:
  • devtools::document() to generates the .Rd files from any updated roxygen comments.
  • codemetar::write_codemeta() to ensures the metadata file is up to date.
  • styler::style_pkg() to ensure consistent code styling that match the guidelines.
  • devtools::check() for a comprehensive package check. I have resolved any warnings or errors, or written them here in the PR, for discussion.
• The code base and the documentation files match (they both reflect any recent changes).
• The title of this PR is clear and self-explantory.
• I have added any appropriate labels to this PR.
• This PR is now ready for review (and I have removed the draft PR status).