[ty] introduce multiline pretty printer (#19979)

Requires some iteration, but this includes the most tedious part --
threading a new concept of DisplaySettings through every type display
impl. Currently it only holds a boolean for multiline, but in the future
it could also take other things like "render to markdown" or "here's
your base indent if you make a newline".

For types which have exposed display functions I've left the old
signature as a compatibility polyfill to avoid having to audit
everywhere that prints types right off the bat (notably I originally
tried doing multiline functions unconditionally and a ton of things
churned that clearly weren't ready for multi-line (diagnostics).

The only real use of this API in this PR is to multiline render function
types in hovers, which is the highest impact (see snapshot changes).

Fixes https://github.com/astral-sh/ty/issues/1000

crates/ty_python_semantic/src/lib.rs

@@ -19,6 +19,7 @@ pub use semantic_model::{
     Completion, CompletionKind, HasDefinition, HasType, NameKind, SemanticModel,
 };
 pub use site_packages::{PythonEnvironment, SitePackagesPaths, SysPrefixPathOrigin};
+pub use types::DisplaySettings;
 pub use types::ide_support::{
     ImportAliasResolution, ResolvedDefinition, definitions_for_attribute,
     definitions_for_imported_symbol, definitions_for_name, map_stub_definition,

crates/ty_python_semantic/src/types.rs

@@ -41,6 +41,7 @@ use crate::types::class::{CodeGeneratorKind, Field};
 pub(crate) use crate::types::class_base::ClassBase;
 use crate::types::context::{LintDiagnosticGuard, LintDiagnosticGuardBuilder};
 use crate::types::diagnostic::{INVALID_AWAIT, INVALID_TYPE_FORM, UNSUPPORTED_BOOL_CONVERSION};
+pub use crate::types::display::DisplaySettings;
 use crate::types::enums::{enum_metadata, is_single_member_enum};
 use crate::types::function::{
     DataclassTransformerParams, FunctionDecorators, FunctionSpans, FunctionType, KnownFunction,