Memory consumption by trimming the rows and cells

[krstak]

Description

By having a lot of rows and columns, memory consumption increases a lot. The reason is that we always allocate a new underlying array instead of re-using the existing one.

Steps to reproduce the issue:

1. By trying to convert a huge amount of rows (30000+) into the xlsx

Describe the results you received:

trimCell issue:

trimRow issue: (append)

Describe the results you expected:

We can reusing the existing underlying array instead of always allocating a new one.

Output of go version:

1.21

Excelize version or commit ID:

v2.7.1

Environment details (OS, Microsoft Excel™ version, physical, etc.):