Refactor AST pretty-printing to allow skipping insertion of extra parens

[Aaron1011]

Fixes #75734
Makes progress towards #43081
Unblocks PR #76130

When pretty-printing an AST node, we may insert additional parenthesis
to ensure that precedence is properly preserved in code we output.
However, the proc macro implementation relies on comparing a
pretty-printed AST node to the captured TokenStream. Inserting extra
parenthesis changes the structure of the reparsed TokenStream, making
the comparison fail.

This PR refactors the AST pretty-printing code to allow skipping the
insertion of additional parenthesis. Several freestanding methods are
moved to trait methods on PrintState, which keep track of an internal
insert_extra_parens flag. This flag is normally true, but we expose
a public method which allows pretty-printing a nonterminal with
insert_extra_parens = false.

To avoid changing the public interface of rustc_ast_pretty, the
freestanding _to_string methods are changed to delegate to a
newly-crated State. The main pretty-printing code is moved to a new
state module to ensure that it does not accidentally call any of these
public helper functions (instead, the internal functions with the same
name should be used).

[rust-highfive]

r? @matthewjasper

(rust_highfive has picked a reviewer for you, use r? to override)

[petrochenkov]

r? @petrochenkov

[Aaron1011]

Let's do a Crater run to be on the safe side.

@bors try

[bors]

⌛ Trying commit 88ef6bd26cd4d9d864295faf26ddd890c51f39f1 with merge 89a6ec545e5f85c102ce8eae663f1abae5e6e8b8...

[bors]

☀️ Try build successful - checks-actions, checks-azure
Build commit: 89a6ec545e5f85c102ce8eae663f1abae5e6e8b8 (89a6ec545e5f85c102ce8eae663f1abae5e6e8b8)

[Aaron1011]

@craterbot check

[craterbot]

👌 Experiment pr-77135 created and queued.
🤖 Automatically detected try build 89a6ec545e5f85c102ce8eae663f1abae5e6e8b8
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[petrochenkov]

@Aaron1011
Could you avoid moving code (e.g. to pprust/state.rs) and changing code in the same commit? It's hard to review this way. The move can be split into a separate commit.

[Aaron1011]

@petrochenkov: I've addressed your comments

[Aaron1011]

@craterbot abort

[craterbot]

🗑️ Experiment pr-77135 deleted!

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[petrochenkov]

Could you avoid moving code

Moving foo_to_string to inherent methods also qualifies as a code move here.
Moving just the file renaming into a separate commit doesn't really change the diff (and its readability) compared to the old state.

[Aaron1011]

@craterbot check crates=https://crater-reports.s3.amazonaws.com/pr-77135/retry-regressed-list.txt p=1

[craterbot]

👌 Experiment pr-77135-1 created and queued.
🤖 Automatically detected try build ee7018e6202e3da222c3f222a29cc4a5abe4a19d
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🚧 Experiment pr-77135-1 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🎉 Experiment pr-77135-1 is completed!
📊 7 regressed and 2 fixed (417 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[Aaron1011]

There are a few actix-web regressions that were missed by the check, due to a weird directory structure or being in another fork (e.g. karyx).

@petrochenkov I could extend the check, but it looks like we've covered nearly all of the regressions. This should should be ready to merge.

[petrochenkov]

@bors r+

[bors]

📌 Commit 9a6ea38 has been approved by petrochenkov

[Aaron1011]

@bors rollup=never

This will cause a (small) amount of breakage, so let's make it easy to bisect.

[bors]

⌛ Testing commit 9a6ea38 with merge 4ba5068...

[bors]

☀️ Test successful - checks-actions, checks-azure
Approved by: petrochenkov
Pushing 4ba5068 to master...