feat(zigbee): Add AC DC ElectricalMeasurement support

[P-R-O-C-H-Y]

Description of Change

This pull request introduces a new Zigbee Electrical measurement endpoint support, containing support for both DC and AC(single or multi phase).

Added 3 new examples showing how the Electrical Measurement can be configured and used.

Tests scenarios

Tested using the new examples flashed on ESP32-C6 and connecting to a coordinator running on HomeAssistant ZHA.

NOTE: DC measurement is currently not supported by HA ZHA - pending PR here: zigpy/zha#453

Screenshot of AC multiphase example in HA

Related links

Closes #11277

[github-actions]

	Messages
📖	This PR seems to be quite large (total lines of code: 1927), you might consider splitting it into smaller PRs

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Test Results

 76 files   76 suites   12m 45s ⏱️
 38 tests  38 ✅ 0 💤 0 ❌
241 runs  241 ✅ 0 💤 0 ❌

Results for commit a42cb64.

[Copilot]

Pull Request Overview

This PR adds support for Electrical Measurement (both DC and AC, single- and multi-phase) in the Zigbee library, along with example sketches, configuration files, and documentation updates.

• Introduces ZigbeeElectricalMeasurement endpoint class with DC and AC measurement APIs
• Registers the new endpoint in core headers/CMakeLists and provides three fully documented examples (DC, AC single-phase, AC multi-phase)
• Supplies CI configs and README updates for each example

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
libraries/Zigbee/src/ep/ZigbeeElectricalMeasurement.h	Defines new endpoint class and measurement enums/APIs
libraries/Zigbee/src/Zigbee.h	Includes new ElectricalMeasurement endpoint header
CMakeLists.txt	Adds implementation source to build
libraries/Zigbee/examples/Zigbee_Electrical_DC_Sensor/*	DC example sketch, CI config, and README
libraries/Zigbee/examples/Zigbee_Electrical_AC_Sensor/*	AC single-phase example sketch, CI config, and README
libraries/Zigbee/examples/Zigbee_Electrical_AC_Sensor_MultiPhase/*	AC multi-phase example sketch, CI config, and README

Comments suppressed due to low confidence (2)

libraries/Zigbee/src/ep/ZigbeeElectricalMeasurement.h:1

• Update the class-level comment to reference ElectricalMeasurement rather than Pressure sensor to accurately describe the new endpoint.

/* Class of Zigbee Pressure sensor endpoint inherited from common EP class */

libraries/Zigbee/src/ep/ZigbeeElectricalMeasurement.h:98

• [nitpick] The field name measure_type is ambiguous; consider renaming to measurement_types_bitmask or measured_types for clarity.

  uint32_t measure_type = 0x0000;