Improve tox.ini testing commands for local development

[emdneto]

Description

Currently, in our tox.ini files, we install the required packages for each command using pip install in the commands_pre section. This leads to unnecessary re-installation of packages every time tox -e py312-test... is run, which increases the overall execution time of tests and creates inefficiencies in the testing process while locally developing.

So, the idea is to move the package installation commands from the commands_pre section to the deps section in the tox.ini file. The deps section is designed to handle package dependencies efficiently, ensuring:

• Caching and reuse: Dependencies will only be installed once when necessary, such as when there are changes in the environment or the dependencies themselves.
• Optimized tox runs: Reduces test run times by avoiding redundant package installations (which is excellent for local development, especially in contrib-repo)

A key advantage of this approach is that it allows the use of tox-uv (a tox plugin that optimizes package installation - very fast) without requiring any additional changes to our tox.ini file. See open-telemetry/opentelemetry-python-contrib#2667