Add an ability to use macro processing functions in message templates.

[ozaryx]

Add an ability to use not only macros in templates, but also macro processing functions. Sometimes you need to pull something out of a macro using a regular expression.
For example,

{EVENT.NAME} = "ora primary DB_TEST,dbtest - status - SLA=1"
{{EVENT.NAME}.regsub("^ora .* ([^ ].*),.*$",\1)} => "DB_TEST"

According to the documentation
https://www.zabbix.com/documentation/6.0/en/manual/config/macros/macro_functions

Now an attempt to use macro functions looks like this

---start cut message---
DB_NAME: {ora primary DB_TEST,dbtest  - status - SLA=1.regsub("^ora .* ([^ ].*),.*$",\1)}
---end cut message---

[ozaryx]

After carefully reading the documentation, I realized that the macro functions are applicable to a limited number of macros.