cabal checks PATH before extra-prog-path

[Mistuke]

Describe the bug
When you have a program that's both on your PATH and in extra-prog-path you can't steer cabal to which one you want locally without modifying your PATH.

This is an issue with pkg-config on Windows because by default global installs of msys2 (such as on appveyor) put the wrong version on your path.

$ cabal v2-build ...

Expected behavior
I expect cabal to use the paths I manually specified in extra-prog-path before the ones in PATH. This allows the use more control over which program they wanted used.

[gbaz]

For simple builds it looks like we already prepend the program path:

cabal/Cabal/src/Distribution/Simple.hs

Line 692 in 0abbe37

pathEnv = maybe (intercalate spSep extraPath)

However, for configure we postpend it:

cabal/Cabal/src/Distribution/Simple/Configure.hs

Line 852 in ba45b8e

searchpath = getProgramSearchPath initialProgramDb

And ditto for v2 configuration:

cabal/cabal-install/src/Distribution/Client/ProjectPlanning.hs

Line 444 in 1d4491f

progdb =

As such I'm going to try to change it in the latter two spots.

[jneira]

We have a pr including tests for non windows systems. However there is no evidence it works for windows: there is no integration test neither a manual test (@Mistuke tried the pr with no success, see #8506 (comment))
Reopening until we have a test for windows