Changes

[IndVars] Fix adding trunc instructions to unwind blocks

Truncate instruction must not be inserted before landing pads.
The insertion point is fixed.

[NFC][utils] Factor remaining APIs under FunctionTestBuilder

Finishing the refactoring started in D93413.

Differential Revision: https://reviews.llvm.org/D93506

[LLD] Rename lld port driver entry function to a consistent name

Libraries linked to the lld elf library exposes a function named main.
When debugging code linked to such libraries and intending to set a
breakpoint at main, the debugger also sets breakpoint at the main
function at lld elf driver. The possible choice was to rename it to
link but that would again clash with lld::*::link. This patch tries
to consistently rename them to linkerMain.

Differential Revision: https://reviews.llvm.org/D91418