Closes https://github.com/zed-industries/zed/issues/59689

Symbolicating the reporter's profile (21s of typing, Windows) showed
`Window::draw` taking 63% of the main thread at ~62 redraws/s (p95 draw
= 40ms), and 30.9% of the *entire* main thread inside
`EditorconfigStore::properties()`:
every `LanguageSettings` lookup — several per frame via
`DisplayMap::tab_size`, `MultiBuffer::language_settings`, indent guides,
and `LspStore::supports_range_formatting` — re-ran the full editorconfig
resolution (ancestor walk plus `ec4rs::Section::apply_to` over every key
of every section) and then cloned the whole `LanguageSettings` struct.
Real-world `.editorconfig` files carry hundreds of irrelevant keys
(`dotnet_*`, `ij_*`, ...), so the per-call map assembly dominated:
`RtlAllocateHeap` 7.3%, `memcmp` 7.0%, `memcpy` 6.6%,
`Properties::find_idx` 5.9% self time.

## Commit 1: resolve only the editorconfig properties Zed reads

- `EditorconfigStore::properties()` now applies only the 7 keys Zed
consumes (`indent_style`, `indent_size`, `tab_width`, `end_of_line`,
`max_line_length`, `insert_final_newline`, `trim_trailing_whitespace`)
instead of materializing every key of every matching section.
- Worktrees with no editorconfig at all now return `None` early instead
of allocating an empty `Properties` and forcing a `LanguageSettings`
clone on every lookup.
- Adds an `editor_render_with_editorconfig` benchmark: maximized window,
file-backed buffer at `src/app/components/editor_pane.ts`, a root
`.editorconfig` shaped after [the second
report](https://github.com/zed-industries/zed/issues/59689#issuecomment-5475124891)
(no `root = true`, a `[*]` section with ~3200 keys, 25 sections with
large `{...}` alternation lists) plus a 4-level nested chain, and a
typing workload (insert/delete + cursor moves).

```
main (770aac345c):      time: [37.905 ms 38.005 ms 38.107 ms]
                        time: [38.069 ms 38.157 ms 38.248 ms]
this commit:            time: [2.8547 ms 2.8618 ms 2.8702 ms]
                        time: [2.8372 ms 2.8435 ms 2.8510 ms]
```

The candidate is ~13x faster.
GPUI frame report over the same workload: window draw p50 12.71 ms →
0.76 ms, p99 23.38 ms → 1.22 ms; frame budget overruns 556 → 0.

## Commit 2: cache resolved `LanguageSettings` per buffer

- `Buffer` and `BufferSnapshot` now hold `resolved_settings:
Arc<LanguageSettings>`, recomputed by a `SettingsStore` global observer.
- Global methods for retrieving the settings are still there, but buffer
only uses them for multi buffer's `language_settings_at` with an
injected language different from the buffer's primary; cold scopes such
as extension API, LSP workspace configuration, server startup still use
the global resolution

Same benchmark, same method, on top of commit 1 (alternated runs, quiet
machine):

```
commit 1:               time: [2.8547 ms 2.8618 ms 2.8702 ms]
                        time: [2.8372 ms 2.8435 ms 2.8510 ms]
this commit:            time: [1.6256 ms 1.6325 ms 1.6403 ms]
                        change: [-42.685% -42.270% -41.854%] (p = 0.00 < 0.05)
                        time: [1.6221 ms 1.6284 ms 1.6352 ms]
```

Window draw p50 0.76 ms → 0.47 ms, p99 1.22 ms → 0.69 ms, max 1.02 ms;
zero frame-budget overruns on both sides.
Combined, the benchmark's per-keystroke cost drops ~23x vs `main`
(37.9–38.2 ms → 1.62–1.64 ms).


Release Notes:

- Improved typing and rendering performance in projects that use
`.editorconfig` files.