feat: Buffer readDiscard

[turuslan]

Buffer class is used by parsers.
Sometimes parser needs to advance read position without copying bytes.
For example, zero-copy parser peeks available bytes(), then consumes some of them and advances read position.

Buffer class hides read position as #off private field.
The only function that advances read position is read(p)/readSync(p), which accept buffer as argument.

// currently available workaround
function readDiscard(buf: Buffer, n: number) {
  buf.readSync({ byteLength: n, set() {} });
}

Go provides https://pkg.go.dev/bytes#Buffer.Next function, which advances read position without copying bytes.
This PR proposes readDiscard(n) (please suggest better name), which doesn't return value.

There is truncate(n) function, which does opposite, it keeps "first N bytes", not "after N bytes"

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.00%. Comparing base (ad7c87b) to head (cd66a8c).

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #7244    +/-   ##
========================================
  Coverage   95.00%   95.00%            
========================================
  Files         617      617            
  Lines       51674    51428   -246     
  Branches     9326     9279    -47     
========================================
- Hits        49093    48860   -233     
+ Misses       2038     2029     -9     
+ Partials      543      539     -4     

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