BREAKING CHANGE(config): map legacy options to `--location` & `--strategy`

[darcyclarke]

• remove --local config
• remove --global-style
• remove --legacy-bundling
• add --strategy config with four reify mode options:
  • hoisted (current default mode)
  • nested (formerly --legacy-bundling mode, where deps are installed in place - no hoisting)
  • shallow (formerly --global-style mode, where only direct deps are installed at top-level node_modules)
  • linked (future isolated mode)
• --global should now set --location=global & --strategy=nested when true
• all relevant code paths should use --location & --strategy in place of their legacy counterparts

[fritzy]

--strategy is actually --install-strategy to avoid confusion with auth configuration.

--global was already setting --location in the CLI. While --global does set --install-strategy=shallow in arborist itself, it does not set --location in arborist directly, but within the npm CLI.