+ Func syntax tree
+ Essential functionality Func formatter
+ A new `codegen` package that includes the updated backend
+ Hacks in the compilation pipeline that allow to use both backends
  which is needed for differential testing.

Needed for bottom-up AST generation; e.g. function definiton might be
generated from the expression that calls it.

See: tact-lang#604

Extended the logic of the context to automatically detect dependencies
between functions based on the given AST. It replicates the previous
`WriterContext` logic, but makes things less "imperative", removing
state variables.

We skip this, because we automatically add the standard Func functions as dependencies, which are not present in the context.

…issing functions

Needs statements, expressions, and a bit of polishing. Then, I'll add
semantical analysis and exhaustive tests of all the items.

Fully tested:
* Asm Functions
* Globals
* Pragmas
* Constants

Partially tested: Function definitions and declarations
Next up: Statements

Broght over identifier tests from the funcId fixing PRs. Almost re-wrote
the universally correct identifier recognition, stuck with underscores
for a bit. Will move past that and finilize all other things, up to (and
perhaps including) expressions + semantics. In the background I'll try
to polish identifiers some more :)

Later on, `FuncAst...` types from `grammar.ts` need to be merged with
ones in `syntax.ts`, in favor of the former

Not all pass due to the complicated things with polymorphic types and
identifiers. To be resolved tomorrow, with semantic actions and
expressions.

…ter each other in asm functions

feat(func-parser): divide polymorphic and non-polymorphic, uniform types

However, I still have to restrain the identifiers — they parse too much.
Then, the `grammar.ts` will be swiftly completed and the parser would be
done. I'll do that ASAP

…ting with underscores

...and/or similar things

Next up: two highest-precedence sets of expressions and rework of
identifiers. Then, if that works out, semantic actions (finally!). If
even that won't, I'm calling FunC "context-sensitive", getting rid of
Ohm and swiftly hand-rolling a recursive descent parsed based on the C++
sources of FunC. *sigh*

…ib.fc and Tact's stdlib

Note, that generic types in variable declarations are temporarily
omitted, as they turn FunC into a context-sensitive grammar. This could
be resolved in the future, by either doing some hacks during syntax
analysis, or by introducing, say, a `decl` keyword into FunC to prefix
all variable declarations: `decl var/_/type(s) ids...`

…the AST construction (mostly typing stuff in), and we're done!