[opt] avoid memcpy when building page

[dataroaring]

PageBuilder finishes a page when the page is full, when the page is
full, its size is greater than page size, so the last row would
trigger an memcpy due to there is not enough space in faststring.

The patch fix the problem by 2 changes:

1. PageBuilder reserves extra bytes
   If the last row is less than extra bytes, then no memory copy is
   triggered.
2. faststring uses malloc/realloc/free rather than new/delete
   realloc can avoid memcopy some times.

The patch is not tested, so please do not merge.

Proposed changes

Issue Number: close #xxx

Problem Summary:

Describe the overview of changes.

Checklist(Required)

1. Does it affect the original behavior: (Yes/No/I Don't know)
2. Has unit tests been added: (Yes/No/No Need)
3. Has document been added or modified: (Yes/No/No Need)
4. Does it need to update dependencies: (Yes/No)
5. Are there any changes that cannot be rolled back: (Yes/No)

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[github-actions]

We're closing this PR because it hasn't been updated in a while.
This isn't a judgement on the merit of the PR in any way. It's just a way of keeping the PR queue manageable.
If you'd like to revive this PR, please reopen it and feel free a maintainer to remove the Stale tag!