Python sync: Fix wheel build failure due to missing README.md

[liorsve]

This PR fixes and reverts most changes made in PR #4714.
PR #4714 attempted to add description to pypi by dynamically reading README.md from the parent directory (./python) at module-level in setup.py since no README exists directly in the glide-sync package directory. However, this approach fails when building from the sdist because:

1. Local wheel builds: When running python3 dev.py build --client sync --wheel, the isolated build extracts the sdist to a temp directory where ROOT.parent no longer points to ./python
2. PyPI source builds: When PyPI attempts to build wheels from the source distribution (when no compatible wheel exists), the same path resolution issue occurs

This PR fixes it by -

1. Declare readme statically in pyproject.toml: Changed from dynamic = ["version", "readme"] to readme = "README.md", allowing setuptools to handle README loading at the correct build phase
2. Copy README.md into package directory: Updated dev.py to copy python/README.md → python/glide-sync/README.md before building, ensuring the file exists at the expected location (this was added to the pypi-cd workflow already in the previous PR)
3. Remove dynamic README handling from setup.py: Removed module-level long_description read since metadata is now properly declared in pyproject.toml

As can be seen in the pypi-cd run below, the tarball artifact produced includes README.md at the package root, and the generated PKG-INFO metadata file contains the full README content with Description-Content-Type: text/markdown, confirming it will be properly displayed as the package description on PyPI.

Issue link

This Pull Request is linked to issue: #4932

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one issue.
• Commit message has a detailed description of what changed and why.
• Tests are added or updated.
• CHANGELOG.md and documentation files are updated.
• Destination branch is correct - main or release
• Create merge commit if merging release branch into main, squash otherwise.