Fix #58532: fix terminal scroll position when opened

[bdrazen]

Fixes #58532

[msftclas]

All CLA requirements met.

[Tyriar]

@dbjelovuk did you gain any insights into the root cause of this while investigating? I suspect a change in xterm.js would be the best fix for this.

[bdrazen]

@Tyriar I've tried approaches like calling the xterm's scrollToBottom() and directly calling syncScrollArea() from the _core object with no success. Definitely seems to be an xterm issue needing further investigation, but figured this could serve as a temporary patch job in the interim.

[bdrazen]

@Tyriar I've made an adjustment to xterm that should allow this to be refactored with a simple this._xterm.syncScrollArea(true) in place of the scroll emit.

Problem stemmed from the viewport's underlying _refresh() not being invoked as the buffer didn't change.

this._xterm._core.viewport._refresh() could work just the same in absence of that xterm update. Just need to add the typings.

[Tyriar]

Fixed in xtermjs/xterm.js#1698