internal/lsp/source: allow users to set new options for network access

These options were added in CL 274532, but it's not possible for users
to actually set them.

Change-Id: I85642ada017f225d4d77e4dfc97fe13847f4091a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/275442
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/lsp/source/options.go

@@ -792,6 +792,12 @@ func (o *Options) set(name string, value interface{}) OptionResult {
 	case "experimentalPackageCacheKey":
 		result.setBool(&o.ExperimentalPackageCacheKey)
 
+	case "allowModfileModifications":
+		result.setBool(&o.AllowModfileModifications)
+
+	case "allowImplicitNetworkAccess":
+		result.setBool(&o.AllowImplicitNetworkAccess)
+
 	case "allExperiments":
 		// This setting should be handled before all of the other options are
 		// processed, so do nothing here.