[FEATURE] Mark legacy sensor drivers as "deprecated"

[linguini1]

Is your feature request related to a problem? Please describe.

Related to #18430 and a few other drivers received recently.

NuttX has decided to move to the new sensor framework/uORB way of writing sensor drivers for consistency + better features, but this is only mentioned on the documentation page for uORB. This results in many contributors missing that information and unfortunately closing their contribution after having dedicated time to writing the driver in the legacy way.

Describe the solution you'd like

As suggested by contributors, we should mark the legacy sensor driver code in the source tree as being "deprecated"/legacy with an in-code comment and possibly a #warning directive. This way, contributors who are using the source-code as a reference for their own driver will be aware that they should reference a newer uORB-style driver instead.

Describe alternatives you've considered

No response

Verification

• I have verified before submitting the report.

[linguini1]

Current plan: add the following after the SDPX identifier/top-of-file comment:

/* WARNING for developers:
 *
 * This driver uses the legacy style of writing sensor drivers for NuttX. The
 * project has since decided to adopt a new sensor framework in order to
 * have a consistent API and feature-set.
 *
 * Sensors which use the uORB framework are typically suffixed "_uorb". You
 * can also visit the documentation about the new sensor framework to learn
 * more.
 */

#warning "This is a deprecated legacy sensor driver."