AP_Proximity: LD06/LD19 gets mode filter

[rmackay9]

This alternative to PR #30050 adds a mode filter to try and remove the noise from the sensor readings when used outdoors

This PR also includes these fixes:

1. comments are slightly improved
2. fix to the distances pushed to the OA database. Previously a distance was pushed for each 2 deg sector but this distance was the shortest distance for the "face" (the "face" is the larger 45 degree sector into which the smaller 2 deg sector falls)
3. constify a local variable
4. improve some definitions (add a confidence definition, remove some unused definitions)

This has not yet been tested on real hardware nor in the simulator

The relevant 4.6.0-beta discussion is here

[Copilot]

Pull Request Overview

This PR adds a mode filter for sensor readings to help reduce noise when operating outdoors while also addressing fixes related to distance reporting and minor comment improvements.

• Introduces a mode filter template specialization for uint16_t values.
• Updates the AP_Proximity LD06 header to include the mode filter and adds a new filter member variable.
• Modifies the distance processing logic in the LD06 source file to apply the filter and pushes corrected distance values to the database.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
libraries/Filter/ModeFilter.cpp	Added template instantiation for ModeFilter<uint16_t,3>.
libraries/AP_Proximity/AP_Proximity_LD06.h	Added include and a new mode filter member; potential type mismatch.
libraries/AP_Proximity/AP_Proximity_LD06.cpp	Updated distance processing to use the mode filter and improved the use of the confidence threshold.

[Copilot]

Pull Request Overview

This PR introduces a mode filter to reduce noise in sensor readings for the LD06 sensor while also addressing miscellaneous fixes related to distance reporting and code improvements.

• Added a new ModeFilter instantiation for uint16_t in the filter library.
• Updated AP_Proximity LD06 sensor processing to apply the mode filter and use confidence thresholds.
• Adjusted the values pushed to the OA database and refined comments and variable definitions.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
libraries/Filter/ModeFilter.cpp	Added a new template instantiation for uint16_t filtering.
libraries/AP_Proximity/AP_Proximity_LD06.h	Included the mode filter header and introduced the filter object.
libraries/AP_Proximity/AP_Proximity_LD06.cpp	Modified distance conversion to use the filter; added confidence threshold check; updated database_push call.

Comments suppressed due to low confidence (1)

libraries/AP_Proximity/AP_Proximity_LD06.cpp:173

• [nitpick] Verify that applying the mode filter to the raw sensor value (in mm) before converting to meters meets the intended measurement accuracy.

const float distance_m = _dist_filt_mm.apply(UINT16_VALUE(_response[i + 1], _response[i])) * 0.001;

[rmackay9]

I've fixed up the autotest and rebased on master. Personally I think this is ready to merge now