refactor(browser): split installation and profile abstractions (#603)

* refactor(browser): split installation and profile abstractions

A Chromium installation shares one master key across its profiles, but
modeling each profile as its own Browser re-derived the key per profile.
Browser now represents one installation holding its profiles and derives
the key once; new types.Profile/ExtractResult/CountResult carry per-profile
results.

* style: gofumpt safari_test.go

* test(chromium): rename shadowed loop var to path

cmd/hack-browser-data/dump.go

@@ -31,7 +31,7 @@ func dumpCmd() *cobra.Command {
   hack-browser-data dump -f cookie-editor
   hack-browser-data dump --zip`,
 		RunE: func(cmd *cobra.Command, args []string) error {
-			browsers, err := browser.PickBrowsers(browser.PickOptions{
+			browsers, err := browser.DiscoverBrowsersWithKeys(browser.PickOptions{
 				Name:             browserName,
 				ProfilePath:      profilePath,
 				KeychainPassword: keychainPw,