Using directory local environment for language servers and other functionality

### Description

Environment providers.

I propose a new struct: `EnvironmentProviderStore`, for the environment providers, which would be used to get the environment for the current directory. This should be implemented in two stages:
a) Implement the API inside of CodeEdit to iron out rough edges, implement support for direnv, venv, asdf and dotenv using it.
b) Create an extension API allowing users to extend CodeEdit with their own environment providers, move existing ones to the extensions

The protocol is as follows:
```swift
protocol EnvironmentProvider {
var displayName { get }
func update_env(_ env: [String : String], for directory: FilePath) async throws -> [String: String]
}
```

Then, based on this protocol, projects should use functions reliant on it to find binaries in path, as well as passing the environment to executed processes

### Alternatives Considered

Install everything globally

### Additional Context

An example implementation for `direnv`
```swift
import Foundation

struct DirenvProvider: EnvironmentProvider {
let displayName = "direnv"

func update_env(_ env: [String: String], for directory: FilePath) async throws -> [String: String] {
let process = Process()
process.executableURL = URL(fileURLWithPath: "/usr/bin/env")
process.arguments = ["direnv", "export", "json"]
process.currentDirectoryURL = URL(fileURLWithPath: directory.string)
process.environment = env

let pipe = Pipe()
process.standardOutput = pipe
process.standardError = Pipe()

try process.run()
process.waitUntilExit()

guard process.terminationStatus == 0 else {
throw DirenvError.commandFailed(exitCode: process.terminationStatus)
}

let data = pipe.fileHandleForReading.readDataToEndOfFile()
guard let jsonString = String(data: data, encoding: .utf8) else {
throw DirenvError.invalidOutput
}

guard let jsonData = jsonString.data(using: .utf8),
let exportedEnv = try JSONSerialization.jsonObject(with: jsonData) as? [String: String] else {
throw DirenvError.jsonParsingFailed
}

var updatedEnv = env
for (key, value) in exportedEnv {
updatedEnv[key] = value
}

return updatedEnv
}
}

enum DirenvError: Error, LocalizedError {
case commandFailed(exitCode: Int32)
case invalidOutput
case jsonParsingFailed

var errorDescription: String? {
switch self {
case .commandFailed(let exitCode):
return "direnv command failed with exit code \(exitCode)"
case .invalidOutput:
return "direnv produced invalid output"
case .jsonParsingFailed:
return "Failed to parse direnv JSON output"
}
}
}
```

This should of course be made to asynchronously execute the direnv process but that's mostly details

Zed implementation for reference (it hardcodes direnv and relies on a shell hook for everything else which is explicitly **not** what I want to do here:
https://github.com/zed-industries/zed/blob/main/crates/util/src/shell_env.rs
https://github.com/zed-industries/zed/blob/main/crates/project/src/environment.rs#L178

### Screenshots

_No response_

从提议的 EnvironmentProvider 协议和 EnvironmentProviderStore 设计开始；issue 中没有指定任何 CodeEdit 文件或测试。使用链接的 Zed shell_env.rs 和 environment.rs 参考作为上下文，然后将工作划分为所述的两个阶段。完成意味着目录本地环境支持 direnv、venv、asdf 和 dotenv，将其传递给相关进程，并且之后可以通过扩展 API 进行扩展。

由索引模型根据 Issue 内容生成。