Adds a minimum estimated size.

Data suggests that estimated instruction size (+ relocation info size)
is linear to bytecode array length. This CL adds a constant for this
equation. The ratio remains the same.

This is important, because we want to increase success rate of
estimation when compiling on-heap.

When off-heap, we round up the assembler buffer to 4kB, so this CL
will only impact JS functions with more than 585 bytecodes, i.e, the
new added constant will be negligible.

Note: Relocation info (for Sparkplug) is usually so small that it is
not useful to have a separate zone for this.

Bug: v8:11872
Change-Id: I789e72f80b970d1f541965e7ae808b61c8174326
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3069155
Auto-Submit: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76144}