feat(sprout): generator variants

[azenla]

Adds variants and exclude rules to generators, so a family of near-identical entries can be declared once instead of copied per combination.

Variants

A generator can declare variant axes. Each axis is a list of choices, and every entry the generator produces is multiplied by every combination of choices, one per axis. A choice sets $<axis> to its name and inserts its own values. The entry name gets the choice names appended.

[generators.linux.bls]
entry.title = "$title ($console-title$mode-title)"
entry.actions = ["boot-linux"]

[generators.linux.variants]
console = [
  { name = "serial", values = { console-options = "console=ttyS0", console-title = "serial" } },
  { name = "graphics", values = { console-options = "", console-title = "graphics" } },
]
mode = [
  { name = "normal", values = { mode-options = "", mode-title = "" } },
  { name = "debug", values = { mode-options = "loglevel=7", mode-title = ", debug" } },
]

This works with any generator kind (bls, list, matrix). Axes are applied in alphabetical order, and choices in the order they are declared. An axis with no choices, or with two choices of the same name, is a configuration error.

Exclude rules

exclude removes generated entries after variants are applied. Each rule maps value names to glob patterns. An entry is dropped when every key in any one rule matches.

[generators.linux]
exclude = [
  { chainload = "*-rescue-*" },
  { console = "graphics", mode = "debug" },
]

Related fixes

• Entry matching for default-entry and the bootloader interface now supports * anywhere in the pattern, not just at the end. When several entries match, the first one in menu order is still used.
• The BLS generator has a new pin-names option, defaulting to true, which is the current behavior. A second BLS generator reading the same directory as autoconfigure used to produce entries with identical names. Setting pin-names = false prefixes them with the generator name instead. Sprout now logs a warning when two entries share a name. Pinned names still get variant suffixes, so a pinned entry with variants is selected with a pattern like <id>-*.
• Prefixing entry names with the generator name moved from main.rs into generators::generate, so variants are built on the final names.

Testing

• New unit tests in edera-sprout-parsing for glob matching, exclude rules and variant combinations.
• cargo clippy -D warnings and cargo fmt --check are clean.