Move get element functionality to a helper (#33327)

Looking around on js components I found out many checks, different expressed but with same purpose.
Some of them are trying to parse string to element, others, jQuery element to js simple nodeElement etc

With this Pr, I am trying to give a standard way to parse an element

So this pr:

* Creates `getElement` helper that tries to parse an argument to element or null
* Changes `isElement` to make  explicit checks and return Boolean 
* fixes tests deficiencies

js/src/tooltip.js

@@ -10,6 +10,7 @@ import * as Popper from '@popperjs/core'
 import {
   defineJQueryPlugin,
   findShadowRoot,
+  getElement,
   getUID,
   isElement,
   isRTL,
@@ -256,7 +257,7 @@ class Tooltip extends BaseComponent {
     const attachment = this._getAttachment(placement)
     this._addAttachmentClass(attachment)
 
-    const container = this._getContainer()
+    const { container } = this._config
     Data.set(tip, this.constructor.DATA_KEY, this)
 
     if (!this._element.ownerDocument.documentElement.contains(this.tip)) {
@@ -385,10 +386,8 @@ class Tooltip extends BaseComponent {
       return
     }
 
-    if (typeof content === 'object' && isElement(content)) {
-      if (content.jquery) {
-        content = content[0]
-      }
+    if (isElement(content)) {
+      content = getElement(content)
 
       // content is a DOM node or a jQuery
       if (this._config.html) {
@@ -518,18 +517,6 @@ class Tooltip extends BaseComponent {
     this.getTipElement().classList.add(`${CLASS_PREFIX}-${this.updateAttachment(attachment)}`)
   }
 
-  _getContainer() {
-    if (this._config.container === false) {
-      return document.body
-    }
-
-    if (isElement(this._config.container)) {
-      return this._config.container
-    }
-
-    return SelectorEngine.findOne(this._config.container)
-  }
-
   _getAttachment(placement) {
     return AttachmentMap[placement.toUpperCase()]
   }
@@ -664,16 +651,14 @@ class Tooltip extends BaseComponent {
       }
     })
 
-    if (config && typeof config.container === 'object' && config.container.jquery) {
-      config.container = config.container[0]
-    }
-
     config = {
       ...this.constructor.Default,
       ...dataAttributes,
       ...(typeof config === 'object' && config ? config : {})
     }
 
+    config.container = config.container === false ? document.body : getElement(config.container)
+
     if (typeof config.delay === 'number') {
       config.delay = {
         show: config.delay,