Linux runtime: overrun detection for real-time timers and for plc execution.

If real-time timer wakes-up PLC thread too late (10% over period), then
warning is logged.

If PLC code (IO retreive, execution, IO publish) takes longer than requested
PLC execution cycle, then warning is logged, and CPU hoogging is mitigated
by delaying next PLC execution a few cylces more until having at least
1ms minimal idle time.

Fix typo in toolchain_gcc.py : LDLAGS -> LDFLAGS

Merged from default

Merge.

SVGHMI: add two more simple widgets to default widget library

Cosmetic fix in plc_debug.c template

Merge.

Modbus plugin: add optional delay between two consecutive modbus requests sent by master/client

Runtime: Add RealTime checkbox in Linux target options to enable PREEMPT_RT scheduling.

Runtime: move LC_NUMERIC locale setting to Beremiz_service.py.

Test: Customize Fluxbox launch to get rid of toolbar in IDE tests.

Tests: Use TESSERACT_LSTM_COMBINED, LSTM + Legacy OCR mode in Sikuli, more stable results.

Merged default in wxPython4 branch

Runtime: Fix bugs in Linux target.

- next occurence absolute time computation failing on 32-bit because of casting
- PLC thread was started before period was set, potentially passing uninitialized timespec to clock_nanosleep()

runtime: Change Linux target to use clock_nanosleep instead of timer (better rt-preempt perf).

Linux runtime: fix thread waiting on wait_RT_to_nRT_signal not being waken-up when delete_RT_to_nRT_signal is invoked.

Tests: docker image needs tesseract4, but opencv lib since sikuli.jar already contains it.

More explicit default value for generic makefile target command. Assume Makfile is located in project_files

IDE: prevent IDE/CLI process surviving to sys.exit() by using deamon threads to monitor external processes output streams.

Tests: allow overriding local host's hostname with BEREIS_LOCAL_HOST env variable.

Tests: IDE: explicitely wait for build success rather than just stdout to become silent.

Tests: Fixed wrong path (relative to $HOME) in CLI tests.

Tests: OPCUA tests can now use OPCUA_DEFAULT_HOST environment variable to force host to something else than "127.0.0.1" or "localhost"

IDE: fix segfault when unselecting network discovery in URI editor

IDE: fix exception when showing project's context menu in case of empty clipboard (wxpython4).

Tests: Fix dockerfile not finding locales.

cosmetic fix

Tests: use expedited termination of IDE with SIGTERM instead of normal close

Work around test not finishing when IDE ask for confirmation on exit when
project is modified.

IDE: When receiving SIGTERM signal, kill runtime befor bailing out without saving.

Purpose is to allow expedited test termination.

Merged default in wxPython4 branch

tests: IDE: own text matching logic for OCR reliability, enhanced ihtml report

SVGHMI: update generated XSLT files

examples: add "csv_read" project to demo CSV access from PLC

py_ext: add CSV file reading POUs in python extension library

SVGHMI: fix input widget sometime messing with font style

Merged default in wxPython4 branch

ST code generator: when including PLCopen TC6 XML libraries (for example py_ext/pous.xml or NativeLib.xml), also includes libraries globals in result

Runtime: add arbitrary file upload to working dir in web interface

SVGHMI: fix double-dispatch happening when using low widget update frequency on variable already being updated with high frequency by other widgets.

Merge

Backed out changeset ddadbdf20e70, no effect on current problem.

GH CI: try reverting to previous version of ubuntu

IDE tests: ensure that file browser idled before entering path in new_project

tests/tools: move comment and remove dead code in Dockerfile

tests: add tesseract training data "tessdata", still trying to enhance OCR reliability in UI tests

tests: attemps to make OCR based hits more stable

Tests: fix path logic in Docker creation script, consequence of previous commit.

Tests: cleanup and tidy docker definitions and scripts