Hello,

This patch brings a comint-like interface for history Isearch to Eshell.
To try it, type 'M-r' in Eshell, and search through the input history
ring incrementally.

Compared to the existing implementation, this patch integrates with
Isearch properly, like what we do for the minibuffer and comint modes.

There are relevant discussions (thank you all for the feedback!) in the
mailing list:

    https://lists.gnu.org/archive/html/emacs-devel/2024-11/msg00069.html

For Jim's concern, I do not think this implementation closes the door
for a history completion interface, as shown by Sean and Juri.

Thanks!

Pengji