Support session from lsp initialization params

[chipsenkbeil]

To support neovim plug-in, we need way to get a session securely. For normal client, the stdin option is most secure, but neovim native lsp doesn't provide control to send a stdin line before initialization.

Instead, we should parse an initialization request first and extract out a session included in initialization params before forwarding it along.

Should be included in initializatianOptions defined in to specification. Those options will be removed from the total provide as if they were never there.

[chipsenkbeil]

Resolved by 69af44c

[github-actions]

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