Prioritize pcov above xdebug

[Zlender]

Pcov is a much faster code coverage driver and in situtation where both Xdebug and pcov are installed it should be used above xdebug in my opinion.

I've tested with a codebase with some 40k lines of code and 4000 tests.

Config	Time	Memory
No coverage	20s	280MB
Pcov only	42s	390MB
Pcov and xdebug with patch	1.44min	410MB
Pcov and xdebug without patch	8min	360MB

It is a change in behavior though as pcov and xdebug might collect different coverage information

[codecov]

Codecov Report

Merging #709 into master will not change coverage.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #709   +/-   ##
=========================================
  Coverage     85.13%   85.13%           
  Complexity      812      812           
=========================================
  Files            32       32           
  Lines          2476     2476           
=========================================
  Hits           2108     2108           
  Misses          368      368

Impacted Files	Coverage Δ	Complexity Δ
src/CodeCoverage.php	73.13% <100%> (ø)	181 <0> (ø)	⬇️

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[sebastianbergmann]

Thank you for your contribution. I appreciate the time you invested in preparing this pull request. However, I have decided not to merge it as I do not think that there is an issue to solve here: simply do not load Xdebug and PCOV at the same time.

[sebastianbergmann]

Changed my mind, thank you for your contribution.

[Zlender]

Thank you.