zulip_tools: Add a get_config_bool to match Puppet logic.

Unfortunately, the existing use of this logic in `process_fts_updates`
cannot switch to using this code, as that code cannot import
zulip_tools.

puppet/zulip/lib/puppet/parser/functions/zulipconf.rb

@@ -6,7 +6,8 @@ module Puppet::Parser::Functions
     output = `/usr/bin/crudini --get #{zulip_conf_path} #{joined} 2>&1`; result = $?.success?
     if result
       if [true, false].include? default
-        # If the default is a bool, coerce into a bool
+        # If the default is a bool, coerce into a bool.  This list is also
+        # maintained in scripts/lib/zulip_tools.py
         ['1','y','t','true','yes','enable','enabled'].include? output.strip.downcase
       else
         output.strip

scripts/lib/zulip_tools.py

@@ -595,6 +595,16 @@ def get_config(
     return default_value
 
 
+def get_config_bool(
+    config_file: configparser.RawConfigParser, section: str, key: str, default_value: bool = False
+) -> bool:
+    if config_file.has_option(section, key):
+        val = config_file.get(section, key)
+        # This list is parallel to puppet/zulip/lib/puppet/parser/functions/zulipconf.rb
+        return val in ["1", "y", "t", "true", "yes", "enable", "enabled"]
+    return default_value
+
+
 def get_config_file() -> configparser.RawConfigParser:
     config_file = configparser.RawConfigParser()
     config_file.read("/etc/zulip/zulip.conf")