[ refactor ] move parser into Idris

[wizard7377]

Description

Currently, the Idris 2 parser is split into three places

1. src/Libraries/Text which defines the core parsing environment (independent of the Idris syntax)
2. src/Parser, which defines part of the Idris syntax
3. src/Idris/Parser.idr and src/Idris/Parser/Let.idr, which define the rest of the parser (and the final general parsing methods)

The last two of these seem like they should be in the same place, preferably in src/Idris/Parser, as they are Idris front-end components. So, as a part of #3369, this is intended to make the parser organization more understandable for new contributors, as well as new syntax

1. Moves Parser.* to Idris.Parser.Core.*
2. Splits up src/Idris/Parser/Basic.idr into src/Idris/Parser/Source.idr src/Idris/Parser/Repl.idr, and makes src/Idris/Parser.idr re-exports all of them.

Ultimately, this means that the directory src/Idris/Parser contains all of the Idris specific parser code, and also splits up the parser to be less large (granted, src/Idris/Parser/Source.idr is still nearly 2000 lines long, but src/Idris/Parser.idr was nearly 3000 lines long).

Apart from this the changes include:

• Exporting some things from src/Idris/Parser/Basic.idr and src/Idris/Parser/Source.idr that are used in one of the other files (as they are now separate)
• Changing all the imports of these modules to have the correct names

While refactors are annoying to deal with and take up time, I believe that this, given its simplicity (almost everything is just copy pasted from one file to another), is worth the time.

I might note that this starts with the following:

[epistemic status: Not very confident on a lot of this. High level should be ok, but lot of details could be wrong]

So the idris2 repo has a lot of parsers, and I spent the last few weeks being confused by which is which. After a lot of grepping, I think this is where they all are and their general purpose. This is mostly just notes from what I found when rewriting the idrall parser, but maybe it’s useful to others.

Self-check

• This is my first time contributing, I've carefully read CONTRIBUTING.md
  and I've updated CONTRIBUTORS.md with my name.
• If this is a fix, user-facing change, a compiler change, or a new paper
  implementation, I have updated CHANGELOG_NEXT.md

[wizard7377]

This is currently failing due to pack having a internal dependency on Idris file structure, so this should be pulled before the pack pr

[dunhamsteve]

It looks like it also breaks idris2-lsp and katla.

[wizard7377]

It looks like it also breaks idris2-lsp and katla.

Fixed!

[gallais]

I'm not sure I see the point of this type of PR:

• it touches a lot of files which makes reviewing involved
• it breaks downstream projects which makes deployment complex
• it breaks everyone's current mental map of what is where

all in the name of "improv[ing] readability", a subjective outcome?

We have fairly limited people power (with e.g. much higher priority structural PRs
opened since March #3513 and not yet fully
merged in) and I'm not sure this kind of shuffling around of things is worth it tbh.

[wizard7377]

Made some updates to the description

[GulinSS]

Working on #3513 to move forward with coming updates

[wizard7377]

Working on #3513 to move forward with coming updates

Agreeed

[GulinSS]

@gallais
@wizard7377

#3513 is ready for review and merge.