Feat: Add completion for Yocto defined variables in embedded languages

[idillon-sfl]

This adds completion items for Yocto variables inside Python datastore functions.

This also add completion items for Yocto tasks inside Python and Shell functions.

Completion items for variable expansions inside Shell regions is waiting for a fix on tree-sitter-bitbake (see PR19)

[deribaucourt]

I only get functions completions in d Python functions instead of variable names:

[idillon-sfl]

I was not handling the case were the string is empty. Should be fixed now.

[deribaucourt]

SImilarly, I don't think completion is handled in bash regions on new line (should suggest commands like echo)
can be done in another PR

[idillon-sfl]

SImilarly, I don't think completion is handled in bash regions on new line (should suggest commands like echo) can be done in another PR

It works on my side. I have these suggestions on empty new lines.

I expect we might want to fine tune some behaviors in the future, thought.