Config to make town square read only (#7140)

* Be able to make Town Square read-only (Disable typing messages for non admins).

* Do not emit UserTypingEvent when TownSquareIsReadOnly and is Town Square.

* Add unit tests for TownSquareIsReadOnly config value and logic.

* Add TownSquareIsReadOnly to System console>Policy. Added Telemetry.

* Add control for TownSquareIsReadOnly=true only for License Enterprise Edition E10 & E20.

* Update en.json

* Update en.json

* Update policy_settings.jsx

* Change config value from TownSquareIsReadOnly to ExperimentalTownSquareIsReadOnly.

* Refactored to simplify. Avoid code repeat and multiple db calls.

utils/config.go

@@ -518,6 +518,7 @@ func getClientConfig(c *model.Config) map[string]string {
 	if IsLicensed() {
 
 		License := License()
+		props["ExperimentalTownSquareIsReadOnly"] = strconv.FormatBool(*c.TeamSettings.ExperimentalTownSquareIsReadOnly)
 
 		if *License.Features.CustomBrand {
 			props["EnableCustomBrand"] = strconv.FormatBool(*c.TeamSettings.EnableCustomBrand)