* Improved heap and PSRAM handling
- Segment `allocateData()` uses more elaborate DRAM checking to reduce fragmentation and allow for larger setups to run on low heap
- Segment data allocation fails if minimum contiguous block size runs low to keep the UI working
- Increased `MAX_SEGMENT_DATA` to account for better segment data handling
- Memory allocation functions try to keep enough DRAM for segment data
- Added constant `PSRAM_THRESHOLD` to improve PSARM usage
- Increase MIN_HEAP_SIZE to reduce risk of breaking UI due to low memory for JSON response
- ESP32 makes use of IRAM (no 8bit access) for pixeluffers, freeing up to 50kB of RAM
- Fix to properly get available heap on all platforms: added function `getFreeHeapSize()`
- Bugfix for effects that divide by SEGLEN: don't run FX in service() if segment is not active
-Syntax fix in AR: calloc() uses (numelements, size) as arguments
* Added new functions for allocation and heap checking
- added `allocate_buffer()` function that can be used to allocate large buffers: takes parameters to set preferred ram location, including 32bit accessible RAM on ESP32. Returns null if heap runs low or switches to PSRAM
- getFreeHeapSize() and getContiguousFreeHeap() helper functions for all platforms to correctly report free useable heap
- updated some constants
- updated segment data allocation to free the data if it is large
- replaced "psramsafe" variable with it's #ifdef: BOARD_HAS_PSRAM and made accomodating changes
- added some compile-time checks to handle invalid env. definitions
- updated all allocation functions and some of the logic behind them
- added use of fast RTC-Memory where available
- increased MIN_HEAP_SIZE for all systems (improved stability in tests)
- updated memory calculation in web-UI to account for required segment buffer
- added UI alerts if buffer allocation fails
- made getUsedSegmentData() non-private (used in buffer alloc function)
- changed MAX_SEGMENT_DATA
- added more detailed memory log to DEBUG output
- added debug output to buffer alloc function
* added boot loop detection and config backup
* automatic OTA rollback if loading backup does not fix it
* added new file handling functions
* adding verification of json files, added config restore at bootup if broken
* added function to compare contents of two files for future use (currently not used)
- prevent settings change if not using private IP address or same subnet
- prevent OTA from differnet subnet if PIN is not set
- ability to revert firmware
- since Update object is accessible even with ArduinoOTA disabled it should possible to use HTTP OTA regardless
- this saves about 12kB while still allowing OTA updates
- HTTP OTA updates can be blocked using PIN or OTA lock
* changed some parameters to "pointer to const", so compiler can better optimize code size and performance - because data behind a const pointer will never be modified by the called function.
* made setPixelColor `const`
* fixed a few potentially uninitialized local vars (the may have random values if not initialized)
* avoid shadowing "state" in handleSerial()
* plus a few very minor improvements
Remove the large stack buffer as we're just going to copy it in to a
heap buffer anyways. Later we can refine the length estimation or use a
rope-style dynamic data structure like DynamicBufferList.
