fix: make point serialization in line with line protocol

[localvar]

1. make point serialization in line with line protocol.
2. replace fmt.Sprintf with strconv.FormatXXX to improve performance.
3. avoid data copying to improve performance.
4. replace unnecessary atomic operations.
5. rename parseXXXX functions as parse is the opposite operation.

[Chenxulin97]

squash your commits into one

[localvar]

the better practice is keeping these commits, because if I squash them into one, I have to make a force push and detroy all the review conversations.

squash could be done when merging the PR as below snapshot shows:

squash your commits into one

[Chenxulin97]

the better practice is keeping these commits, because if I squash them into one, I have to make a force push and detroy all the review conversations.

squash could be done when merging the PR as below snapshot shows:

squash your commits into one

you are right , thanx