Add comprehensive documentation for both tag-based routing and the new conditional routing feature. Fixes #2199. (#2200)

* Updated to include new input plugin doc for Windows System Statistics. Applies to #2139.

Signed-off-by: Eric D. Schabell <eric@schabell.org>

* Updated to include new input plugin doc for Windows System Statistics. Applies to #2139.

Signed-off-by: Eric D. Schabell <eric@schabell.org>

* Lint fix for winstat input plugin doc fix.

Signed-off-by: Eric D. Schabell <eric@schabell.org>

* pipeline: router: add conditional routing documentation

Add comprehensive documentation for both tag-based routing and
the new conditional routing feature introduced in Fluent Bit 4.0.

- Document tag-based routing with basic matching, wildcards, and regex
- Document conditional routing with per-record evaluation
- Include comparison operators and condition syntax
- Add examples for routing by severity, service name, and regex patterns
- Provide guidance on choosing between routing approaches

Fixes #2199.

Signed-off-by: Eric D. Schabell <eric@schabell.org>

* Review edits applied to routing doc.

Signed-off-by: Eric D. Schabell <eric@schabell.org>

* Typo fix applied to routing doc.

Signed-off-by: Eric D. Schabell <eric@schabell.org>

* Fixing incorrect version reference for conditional routing doc.

Signed-off-by: Eric D. Schabell <eric@schabell.org>

* pipeline: router: add metrics and traces routing examples

Add conditional routing examples for metrics and traces signals:

- Route metrics by name pattern (CPU, memory metrics)
- Route traces by service name and span attributes
- Route multiple signal types (logs, metrics, traces) in one config

Signed-off-by: Eric D. Schabell <eric@schabell.org>

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Signed-off-by: Eric D. Schabell <eric@schabell.org>

Author: eschabell