feat: update user configuration example and add development package support

- Enhanced the user.depot.toml.example file with additional comments and options for user-local preferences.
- Bumped version from 0.35.0 to 0.35.1 in meson.build.
- Introduced a new option for DEPOT_DEVELOPMENT_PACKAGE in meson_options.txt.
- Added functions to handle the requested development package in build_options.rs.
- Updated various builder files (autotools.rs, cmake.rs, custom.rs, meson.rs, perl.rs) to support passing build flags.
- Implemented checks for the required development package during source builds in commands.rs and commands/build_cmd.rs.
- Added tests to ensure the correct behavior of development package requirements and source build warnings.
- Modified manual source handling in source/mod.rs to validate local manual sources before proceeding with builds.
- Updated cargo build and test scripts to accept a new development package argument.
- Added VSCode settings to disable automatic configuration on open.

contrib/depot.d/package.toml

@@ -1,6 +1,19 @@
 [package]
-# System-wide package overrides. Example: set default provides or package metadata
-# name = ""
+# Example /etc/depot.d/package.toml
+#
+# System-wide package metadata overrides. Use this sparingly: this is best for
+# policy defaults or local compatibility shims, not for rewriting package specs.
 
-# Example: provide a virtual runtime package name to satisfy runtime deps
+# Example fields you might override globally in a controlled environment:
+# homepage = "https://mirror.example.org/packages"
+# license = ["MIT"]
+
+# Example: provide a virtual package name to satisfy dependency expressions.
+# This can be useful on systems with a local compatibility package.
 # provides = ["filesystem"]
+
+# Example: declare that local packages replace an older naming scheme.
+# replaces = ["old-filesystem"]
+
+# Example: force a conflict relationship across locally maintained packages.
+# conflicts = ["legacy-filesystem"]