Feat/methodswith dot completion

[xgdgsc]

Fixes #2679 . Works together with julia-vscode/LanguageServer.jl#1210.

A quick demo of concept. Need runtime completion enabled.

Still work needed:

• additional edit to delete previous identifier.
• performance issue when using lots of modules
• move cursor to middle of ",)"
• better way of extracting identifier.
• whether allow custom setting of REPL completion promise timeout.

For every PR, please check the following:

• End-user documentation check. If this PR requires end-user documentation, please add that at https://github.com/julia-vscode/docs.
• Changelog mention. If this PR should be mentioned in the CHANGELOG, please edit the CHANGELOG.md file in this PR.

[xgdgsc]

I' ve used this for months just fine. @pfitzseb What' s your opinion on this? Any plan on merging or what needed changing for merging? Judging from https://discourse.julialang.org/t/allowing-the-object-method-args-syntax-as-an-alias-for-method-object-args/62051/218?u=xgdgsc . There could be a lot of people need this for coming from OOP or working together with OOP languages.

[3f6a]

Please consider adding a setting to disable this feature if desired. It's possible some users might not want to have a list of suggestions including methods that can apply to a given value.

[ParadaCarleton]

@pfitzseb short reminder on this; do you think it could be merged before the next VSCode update?