Update/reorder git instructions in Developer's Guide

[mkoeppe]

(from #33088)

In the developer guide, move "git the hard way" earlier and present "git-trac" only as an additional convenience.
Also note that the first configuration using sagetrac-mirror is not recommended for users who use VS Code (#33589 comment:13)

Depends on #33088

CC: @tobiasdiez @sagetrac-tmonteil @seblabbe @dimpase @yuan-zhou

Component: documentation

Author: Matthias Koeppe

Branch/Commit: aa9faaa

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/33648

[mkoeppe]

Branch: u/mkoeppe/update_reorder_git_instructions_in_developer_s_guide

[mkoeppe]

Author: Matthias Koeppe, ...

[mkoeppe]

Commit: 88b04d4

[mkoeppe]

Last 10 new commits:

b46c953	README: Document --enable-editable and --enable-download-from-upstream-url
a3ffe84	README.md: Instructions for Apple Silicon
d7708df	README.md: Restructure macOS prep instructions
2e1d22d	src/doc/en/installation/source.rst: Remove instructions for Solaris, AIX, HP-UX
9ca39a2	README.md: Point to developer guide for git details
f1e1166	src/doc/en/installation/source.rst: Point to README.md for step-by-step instructions
3f6c6e0	src/doc/en/developer/workspace.rst: Link to Trac #30500
8716d80	src/doc/en/installation/source.rst: Update required venv Python extension modules from build/pkgs/python3/spkg-configure.m4
f4c3604	Merge #33088
88b04d4	src/doc/en/developer/manual_git.rst: Do not recommend mixed sagetrac-mirror / trac operation when using VS Code

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

fc7aa4f	src/doc/en/developer/advanced_git.rst: Mention git log --first-parent
aa9faaa	src/doc/en/developer: move "git the hard way" earlier, present "git-trac" only as an additional convenience

[sagetrac-git]

Changed commit from 88b04d4 to aa9faaa

[mkoeppe]

Changed author from Matthias Koeppe, ... to Matthias Koeppe

[dimpase]

Reviewer: Dima Pasechnik

[dimpase]

comment:6

lgtm

[mkoeppe]

comment:8

Thanks!

[vbraun]

Changed branch from u/mkoeppe/update_reorder_git_instructions_in_developer_s_guide to aa9faaa