feat: add resolve.preserveSymlinks option

[ygj6]

Description

fix #4556, #2405.

Since I don't know much about preserve-symlinks, I've been working on this it for the past few days,I will add test cases and PR details later.
refer:
esbuild#preserve-symlinks,
webpack#resolve.symlinks
node#preserve-symlinks

This commit(feat: add resolve.preserveSymlinks option) focuses on module dependencies,

vite/packages/playground/preserve-symlinks/package.json

Lines 10 to 12 in deca9fb

	"dependencies": {
	"@symlinks/moduleA": "link:./moduleA"
	}

This commit(feat: properly resolve symbolic links that depend on imports) focuses on dependency imports

vite/packages/playground/preserve-symlinks/moduleA/src/index.js

Line 1 in deca9fb

import { data } from './data'

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[dreitzner]

Looks good and seems to have all the changes in the right places. The svelte (-kit) community thanks you 🥳

[Shinigami92]

Is it possible to add tests?

[ygj6]

Is it possible to add tests?

done

[patak-dev]

@ygj6 we discussed this PR with the team and agreed that we should follow other bundlers/tools here, so this PR is approved to be merged.

Since the default would be to now resolve the symlinks (same as in other tools), I think we should include this one in the beta for 2.6 so we give the ecosystem an opportunity to give us feedback.

[bluwy]

In #4634, I added a new nestedResolveFrom function which uses resolveFrom under-the-hood. We might want to update that function too:

vite/packages/vite/src/node/utils.ts

Line 71 in 284170e

export function nestedResolveFrom(id: string, basedir: string): string {

with a preserveSymlinks parameter as well. Don't think we need the ssr parameter.

[ygj6]

Done, thank you for the reminder.

[Shinigami92]

Before merging see @bluwy https://github.com/vitejs/vite/pull/4708/files#r706991758 and at least give they an answer 🙂

[ygj6]

Recently there was a problem with the mailbox, did not deal with this PR in time, thank you all review 😄.

[patak-dev]

Thanks for implementing this feature @ygj6, we have now merged it in preparations for vite 2.6-beta

[zengxiaoluan]

Is preserveSymlinks possible to specify a particular file or directory to make effects?