feat: Add LSP 3.17 InlayHint features (resolve, textEdits, label parts)

[takeokunn]

Summary

Extends lsp-mode's InlayHint support with LSP 3.17 specification features, addressing #4775.

• Add inlayHint/resolve support with resolveSupport capability advertisement for textEdits and tooltip
• Add lsp-inlay-hint-accept interactive command that applies a hint's textEdits (resolving lazily via inlayHint/resolve if needed)
• Add InlayHintLabelPart rendering with per-part tooltip, location (click-to-navigate), and command (click-to-execute)
• Add interactive mouse handler with three-tier click precedence: label part location → label part command → hint accept
• Add tooltip and data field support on InlayHint type
• Add :cancel-token to prevent stale async request accumulation
• Add 3 new mock-server tests for hint data storage, label parts, and keymap presence

Changes

File	Description
lsp-mode.el	New functions (lsp-inlay-hint-accept, lsp--inlay-hint-resolve, lsp--inlay-hint-mouse-handler, lsp--inlay-hint-label-part-string, lsp--inlay-hint-tooltip-text), capability registration,
client capability advertisement, keymap, keybinding (s-l a i)
lsp-protocol.el	Add InlayHintOptions type; extend InlayHint with :textEdits :tooltip :data; add InlayHintLabelPart with :tooltip :location :command
test/lsp-mock-server-test.el	3 new ERT tests for inlay hint data, label parts, and keymap
test/mock-lsp-server.el	Enable resolveProvider in mock server capabilities
CHANGELOG.org	Feature entry under Unreleased 9.0.1

Test plan

• 3 new ERT tests pass (lsp-mock-server-inlay-hint-stores-data, lsp-mock-server-inlay-hint-label-parts, lsp-mock-server-inlay-hint-has-keymap)
• Byte-compilation clean (only pre-existing docstring width warning at line 2277)
• Manual: enable lsp-inlay-hints-mode, verify hints render with tooltips
• Manual: click inlay hint label part with location → navigates to definition
• Manual: invoke lsp-inlay-hint-accept on hint with textEdits → edits applied
• Manual: invoke lsp-inlay-hint-accept on hint without textEdits → resolves via inlayHint/resolve

[jcs090218]

LGTM. :)