fix(fmt): ensure leading blank lines are always removed

[0xrusowsky]

Motivation

closes #12000

Solution

ensure leading blank lines are always removed, even when there are no items in the source

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[0xrusowsky]

@0xalpharush i was unable to repro the issue with contracts that had some source items:

$ echo "\n\ncontract Test {}" > test.sol

$ forge fmt test.sol --check
Warning: This is a nightly build of Foundry. It is recommended to use the latest stable version. To mute this warning set `FOUNDRY_DISABLE_NIGHTLY_WARNING` in your environment.

Diff in src/test.sol:
1        |-
2        |-
3   1    | contract Test {}

please confirm that you were exploring edgecases when the source code only contains cmnts, and that your repro wasn't just a minimal repro from a scenario with actual code.

with the proposed fix, leading blank lines are always removed, even when there is no actual code (just cmnts)

$ echo "\n\n" > test.sol

$ ../../foundry/master/target/release/forge fmt --check
Diff in src/test.sol:
1        |-
2        |-
3        |-

$ echo "\n\n// this is a cmnt" > test.sol

$ ../../foundry/master/target/release/forge fmt --check
Diff in src/test.sol:
1        |-
2        |-
3   1    | // this is a cmnt

[DaniPopes]

can we add a test?

[0xalpharush]

@0xrusowsky It is an edge case

[grandizzy]

lgtm