Revert "Grids: uses const paramterers for strings where applicable. Patch by...

Revert "Grids: uses const paramterers for strings where applicable. Patch by Alexey Torgashin. Issue #39851."

This reverts commit 72344a65.

These changes break compatibility (change signatures of virtual
methods), potentially unsafe (these strings can be potentially changed
through user callbacks and this will lead to crashes) and provide very
little (if at all) performance improvements.

(cherry picked from commit dbfbdee4)