lua: simple snippet support in the completion items (#12118)

Old behavior is: foo(${placeholder: bar, ...)

with lots of random garbage you'd never want inserted.

New behavior is: foo(bar, baz) 

(which maybe is good, maybe is bad [depends on user], but definitely better than it was).

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* Implement rudimentary snippet parsing

Add support for parsing and discarding snippet tokens from the completion items.

Fixes #11982

* Enable snippet support

* Functional tests for snippet parsing

Add simplified real-world snippet text examples to the completion items
test

* Add a test for nested snippet tokens

* Remove TODO comment

* Return the unmodified item if the format is plain text

* Add a plain text completion item

0 files changed, 0 insertions, 0 deletions