perf: use faster 0.11 vim.validate

[iguanacucumber]

this PR replaces vim.validate with it's new 0.11 implementation, that is ~36 000% faster, so it's as fast as no doing no validation at all ( nvim core PR )
This PR takes codes from an indent-blankline PR
Do not merge this right now, since this is only for 0.11

[antonk52]

If the validate function signature is the same, why not introduce a backward compatible util function that can work for both older nvim version and nvim 0.11 and newer? Something along the lines of

utils.validate = vim.fn.has('nvim-0.11') == 1 and fastValidate or vim.validate

this will allow to use the same function across the codebase. Once nvim 0.10 support is dropped this util will no longer be needed

[iguanacucumber]

From the author in PR 487:

I'll wait for 0.11 to release before merging, since I'd rather not maintain two different code paths for keymaps

[Saghen]

~0.16ms shaved off 😎