perf(linter/plugins): provide loc via prototype (#14552)

#14355 added a getter for `loc` to all AST nodes in Oxlint's JS-side AST. Unfortunately it turned out to have been a massive perf hit.

Reduce the cost by adding `loc` field to nodes via prototype, rather than adding a getter to each object individually.

This does not entirely remove the cost of `loc`, but reduces it from about 300% perf hit to around ~20% (measured by Oxlint's performance linting VS Code repo with a simple JS plugin).

Author: overlookmotel