script|layout: Do not force restyle when doing script queries (#37677)

Instead of doing a restyle whenever layout is requested, only do one if
script believes that the `Document` has changed in a way that needs a
restyle. In addition, track the different reasons this might be the
case. This will be used later to provide better debugging output.

In layout, when a restyle isn't requested, provide:
 - an early return if layout is up-to-date enough for the reflow goal.
 - skipping restyle and reflow if it isn't necessary.

Testing: This should not change observable behavior, and thus is covered
by existing tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/shared/layout/Cargo.toml

@@ -13,6 +13,7 @@ path = "lib.rs"
 
 [dependencies]
 base = { workspace = true }
+bitflags = { workspace = true }
 app_units = { workspace = true }
 atomic_refcell = { workspace = true }
 compositing_traits = { workspace = true }