Remove cairo dependence on which command and failing if gtkdocize isn't installed.

[Renari]

Specify library name and version: cairo/all

The cairo package will fail to build if you don't have which installed, it also appears that it will fail without the gtkdocize command, despite autogen.sh appearing to check for the command prior to running it. autogen.sh is a fairly simple script so I moved it's functionality into the conanfile.

fixes #5674

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[ghost]

I detected other pull requests that are modifying cairo/all recipe:

• cairo: modernize + add gtk-doc-stub build requirement #7156

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[Renari]

Hm, it looks like the gtkdoc issue originates from autoconf (which is why builds are failing).

spack/spack#23964

Same issue as above, looks like their workaround was to define GTKDOCIZE to point to echo.

[SSE4]

yes, please keep the formatting, if possible

[conan-center-bot]

All green in build 7 (fd2b3f759d750176604efda0e8464246e647ed25):

• cairo/1.16.0@:
  All packages built successfully! (All logs)

• cairo/1.17.2@:
  All packages built successfully! (All logs)

• cairo/1.17.4@:
  All packages built successfully! (All logs)