Machine readable syntax specification

[jsproz]

Closes #3686

Description

Added a machine readable syntax specification for the Cadence language and a Syntax Notation document.

---

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[github-actions]

Cadence Benchstat comparison

This branch with compared with the base branch onflow:master commit 24783e3
The command for i in {1..N}; do go test ./... -run=XXX -bench=. -benchmem -shuffle=on; done was used.
Bench tests were run a total of 7 times on each branch.

Collapsed results for better readability

[turbolent]

Nice work!

[turbolent]

Did another pass over types as requested. Mainly the precedence rules need to be encoded properly, and the only other thing is the intersection types.

Also did another pass over all declarations, and left a few minor comments, especially regarding what types are allowed.

Will do another pass over expressions tomorrow.

[turbolent]

Did another pass reviewing the expression parsing. Looks good, a couple notes.

Note that some expressions need newline differentiation to resolve ambiguities when expressions are used as statements, see the "(* if no line terminator ahead *)" comments in the expression rules of the EBNF grammar, like

cadence/docs/cadence.ebnf

Line 457 in 5364220

| postfixExpression (* if no line terminator ahead *) invocation

.

For example:

foo(bar) // invocation

foo    // identifier expression
(bar)  // parenthesized expression

[turbolent]

Looks good! Only a couple comments to resolve and then we can merge what we have so far.

@SupunS Could you please take a final look?

[SupunS]

Aren't these keywords also tokens? i.e: shouldn't be <accessKeyword>?