also fix test entry incorrectly using an already escaped string

Make every available call site 'private'
e.g. typing command in telnet no longer prints to serial or WebUI

Serial input is now optional, see `TERMINAL_SERIAL_SUPPORT`.
Telnet using async server is a proper Stream now.
WebUI, MQTT and HTTP input is allowed to inject multiple lines at once.

Modernize our helper classes and remove legacy 2.3.0 quirks.
Replace global Terminal object and allow to separately
split, parse ARGV list and perform command search and invocation with
standalone function calls.
(but, notice that we still depend on a globally shared 'commands' list)

This greatly reduces used RAM (but, slightly increases our ROM).

Update our test suite to use namespaces and new calling convention.

https://gitter.im/tinkerman-cat/espurna?at=6302c2f2cf6cfd27af20f01b
should be toggle, same as the others

tnx to @luismaranesi

https://docs.platformio.org/en/latest/core/userguide/cmd_check.html

cannot depend on checkprogsize, since it depends on .elf and not .bin

also, compare with the block-aligned size
add notes about reserved space

warning might become annoying, though :)

https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests

from the pending ESP8266 Core PR

updates scripts to be a post action
rename redefined symbols to stubs

store objcopy of these extra symbols and .map from the linker
distribution will have an extra debug .zip file that could be used with
the exception decoder

also fixes relative paths in the build-and-copy
(although, yet again loses the pio target in the gui)

in case rare errors sneak up, do not force into unstable mode
previously removed rtcmem special case allows us to continue

missing stringview key checks
fix template specialization order when building single source
update left-over modules that werent using espurna { ... }

execute multiple transition-initiating functions
when we don't do any transitions or have value changes queued

main application for right now is a simple notification
routine that consists of N single channel on->off transitions

make our string comparisons nicer
also clean-up namespaces for storage access

- reduce number of resets that triggers unstable mode
- introduce a reboot reason for stability counter
  which only gets handled on soft-reset
- allow to forcibly change to either stable or unstable mode
  more explicit terminal comands to leave or enter either mode

rework more namespaces to use `espurna` root
makes internal references much easier (and shorter)

view class is not specific to settings, could use it across the app
remove duplicate code from IR

also fix invalid header accessor, toString() returns the whole HTTP
request string as `Host: blabla\r\n`

new-lib does not appear to work very well with 2 kHz

restore pinMode(..., OUTPUT)
manually set initial duty

when target duty is either zero or at the driver limit, forcibly
stop the waveform / pwm driver via a sort-of private function call

resolve #2532