Switch deprecated 'filePath' property to 'uri'

[Steve Yegge]

The ProtocolTextDocument used in the agent protocol has renamed the filePath field to uri and deprecated filePath.

I've updated JetBrains and Emacs to use 'uri', and we need to update Neovim as well. Here are the spots it appears:

lua/tests/cody_lifecycle_spec.lua:47 assert(string.find(opened.params.filePath, "README.md"), "Did not send correct filename")
lua/tests/cody_lifecycle_spec.lua:62 assert(string.find(deleted.params.filePath, "README.md"), "Did not close correct filename")
lua/tests/cody_lifecycle_spec.lua:74 and string.find(msg.params.filePath, "Cargo.toml")
lua/tests/cody_lifecycle_spec.lua:84 and string.find(msg.params.filePath, "Cargo.toml")
lua/tests/cody_lifecycle_spec.lua:91 string.find(changed.params.filePath, "Cargo.toml"),
lua/sg/cody/protocol.lua:35 filePath = name,
lua/sg/cody/protocol.lua:96 if not doc.filePath then
lua/sg/cody/rpc.lua:462 { filePath = file, position = { line = line, character = character } },
lua/sg/private/find_artifact.lua:7 local artifact_file = require("plenary.debug_utils").sourced_filepath()
lua/sg/private/data.lua:40 local plugin_file = require("plenary.debug_utils").sourced_filepath()
lua/sg/types.lua:78 ---@field filePath string
lua/sg/types.lua:183 filePath: string