[pgAdmin4][Patch]: Macros for the functions module

Hi,

Please find attached patch for the Security Labels, Privileges and
Variables macros for the functions modules.

*Usage of the macros:*

*Security labels:*

SECLABLE.SET(conn, 'FUNCTION', func_name, provider, security_label,
func_schema, func_args)

SECLABLE.UNSET(conn, 'FUNCTION', func_name, provider, func_schema,
func_args)

*Privileges:*

PRIVILEGE.SET(conn, 'FUNCTION', grantee, func_name,
privileges_without_grant, privileges_with_grant, func_schema, func_args)

PRIVILEGE.UNSETALL(conn, 'FUNCTION', grantee, func_name, func_schema,
func_args)

*Variables:*

VARIABLES.SET(conn, 'FUNCTION', func_name, options, func_schema, func_args)

VARIABLES.UNSET(conn, 'FUNCTION', func_name, options, func_schema,
func_args)

Thanks,
Khushboo