Implemented support for filters and removable routes in ESP8266WebServer

[ayushsharma82]

This PR implements filters and removable routes in ESP8266 arduino core, making it API compatible with recent changes to ESP32 WebServer API.

Reference (Recent additions to ESP32 WebServer API):

• https://github.com/espressif/arduino-esp32/pull/9832
• https://github.com/espressif/arduino-esp32/pull/9842
• https://github.com/espressif/arduino-esp32/pull/9851

Noteable Changes:

1. Request Filters (setFilter)
2. Removable Routes (removeRoute, removeHandler, _removeRequestHandler)

[ayushsharma82]

@me-no-dev , Please review this as well.

[mcspr]

@me-no-dev , Please review this as well.

Not an Espressif repo (maybe ping @d-a-v). Will merge based on esp32 review, though. Also, please take a look at 'doc/' and WebServer's 'README.md' and make sure everything is up-to-date w/ web documentation related to WebServer

[ayushsharma82]

Oh. I thought me-no-dev is a maintainer in this repo too.

I'll check documentation.

[me-no-dev]

Oh. I thought me-no-dev is a maintainer in this repo too.

Long time ago :)

[ayushsharma82]

@mcspr , @d-a-v,

ESP32 PRs are merged therefore this PR is ready for review & merger as well.

[ayushsharma82]

Any idea why LwIP CI tests are failing? Compiling on Arduino IDE locally doesn't show any error.

[mcspr]

Multiple libraries were found for "WiFi.h" Used: /home/runner/work/_temp/arduino_ide/libraries/WiFi Not used: /home/runner/Arduino/hardware/esp8266com/esp8266/libraries/ESP8266WiFi

[ayushsharma82]

Great! Everything compiles now, what should we do about style test?