feat: Add central logging pragma (#843)

## Summary

* Definition and use of a central LOG function, that can later be
extended or completely be removed (for public use where debugging
information may not be required) to save flash by suppressing the
-DENABLE_SERIAL_LOG like in the slim branch

* **What changes are included?**

## Additional Context
* By using the central logger the usual:
```
#include <HardwareSerial.h>
...
  Serial.printf("[%lu] [WCS] Obfuscating/deobfuscating %zu bytes\n", millis(), data.size());
```
would then become
```
#include <Logging.h>
...
  LOG_DBG("WCS", "Obfuscating/deobfuscating %zu bytes", data.size());
```
You do have ``LOG_DBG`` for debug messages, ``LOG_ERR`` for error
messages and ``LOG_INF`` for informational messages. Depending on the
verbosity level defined (see below) soe of these message types will be
suppressed/not-compiled.

* The normal compilation (default) will create a firmware.elf file of
42.194.356 bytes, the same code via slim will create 42.024.048 bytes -
170.308 bytes less
* Firmware.bin : 6.469.984 bytes for default, 6.418.672 bytes for slim -
51.312 bytes less


### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _NO_

---------

Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

platformio.ini

@@ -54,15 +54,31 @@ extends = base
 build_flags =
   ${base.build_flags}
   -DCROSSPOINT_VERSION=\"${crosspoint.version}-dev\"
+  -DENABLE_SERIAL_LOG
+  -DLOG_LEVEL=2 ; Set log level to debug for development builds
+
 
 [env:gh_release]
 extends = base
 build_flags =
   ${base.build_flags}
   -DCROSSPOINT_VERSION=\"${crosspoint.version}\"
+  -DENABLE_SERIAL_LOG
+  -DLOG_LEVEL=0 ; Set log level to error for release builds  
 
 [env:gh_release_rc]
 extends = base
 build_flags =
   ${base.build_flags}
   -DCROSSPOINT_VERSION=\"${crosspoint.version}-rc+${sysenv.CROSSPOINT_RC_HASH}\"
+  -DENABLE_SERIAL_LOG
+  -DLOG_LEVEL=1 ; Set log level to info for release candidate builds  
+
+[env:slim]
+extends = base
+build_flags =
+  ${base.build_flags}
+  -DCROSSPOINT_VERSION=\"${crosspoint.version}-slim\"
+  ; serial output is disabled in slim builds to save space
+  -UENABLE_SERIAL_LOG
+