Use crafts own python for pip

Motivation

Use our own python instead of the system python for most build tasks. This eliminates incompatibilities etc.

Problems

Bootstrapping.

We basically would need to move python and its deps to the craft repo. We'd need to build all the python deps during bootstrapping.

retending core/cacert: 2023-01-10
pretending dev-utils/7zip-base: 23.01-1
pretending dev-utils/cmake-base: 3.23.3
pretending dev-utils/kshimgen: master
pretending dev-utils/7zip: latest
pretending dev-utils/cmake: latest
pretending dev-utils/git: latest
pretending dev-utils/m4: 1.4.19
pretending dev-utils/sed: 4.7
pretending dev-utils/perl: 5.36.0
pretending dev-utils/autoconf: 2.71-2
pretending dev-utils/automake: 1.16.3-1
pretending dev-utils/libtool: 2.4.7
pretending dev-utils/create-dmg: 1.2.1
pretending dev-utils/ninja: 1.11.1-1
pretending craft/craft-blueprints-kde: dev-2023.12.21
pretending libs/libbzip2: 1.0.6-4
pretending libs/expat: 2.2.10-5
pretending libs/zlib: 1.3
pretending libs/openssl: 3.1.4
pretending libs/liblzma: 5.2.3
pretending dev-utils/pkg-config: 0.29.2
pretending libs/icu: 71.1
pretending libs/libxml2: 2.10.3-3
pretending libs/gettext: 0.22.3-1
pretending libs/sqlite: 3.42.0
pretending libs/libffi: 3.3-2
pretending libs/python: 3.11.5
pretending python-modules/pip-system: master
pretending python-modules/virtualenv: master
pretending python-modules/pip: master
pretending dev-utils/python3: 3-3
pretending virtual/base: 0.2
pretending virtual/craft-blueprints-kde-base: 0.1
pretending craft/craft-core: dev-2023.12.21
pretending craft/craft-blueprints-community: master-2023.12.21

Related: craft-blueprints-kde!759 (merged) @jlskuz @bcooksley