Add option for TeamCity reporter to report SECTIONs

**Description**
The JUnit reporter reports SECTIONs.
The TeamCity reporter does not.
Not sure if reporting SECTIONs should always be enabled, but could there be at least an option?

Except for this, I would very much like to use the TeamCity reporter, since it seems to use a lot less memory compared to the JUnit reporter (10 MB vs. 4 GB in my case).

**Additional context**
Tried with latest version, Catch2 2.11.1.

**Compare JUnit report:**

**...with TeamCity report:**

Start by locating the JUnit and TeamCity reporter implementations and comparing how each handles SECTIONs. Determine how a TeamCity option should be exposed, then verify that enabling it reports SECTIONs while preserving existing behavior when disabled.

Written by the indexing model from the issue text.