docs(wiz): describe the asset exposure the Wiz connector reports

[blakeaowens]

Description

Adds an "Asset Exposure" section to the Wiz connector page (docs/content/connectors/toolreference/wiz.md).

It describes what the connector now reports to Asset Exposure:

• network exposure paths, and which exposure tier each kind of path records (public internet, a constrained internet source or public custom range, a cross-account, VPN or private custom-range path, and nothing for a path inside the resource's own cloud account), with the resource, port range and protocol as evidence;
• the vulnerable-asset exposure fields, which follow the Vulnerability Findings selection;
• that network exposure is read on every sync regardless of Import Finding Types and never becomes a finding;
• that a path Wiz stops reporting ages out after 30 days, and that a service account that cannot read network exposure falls back to the vulnerable-asset fields.

English only; the language copies are generated.