item.update(item_properties={"typeKeywords': "values"}) fills in default values

**Describe the bug**
When providing an update to the `typeKeywords` key, if appropriate values are not provided, then a series of default values are inserted into the item's `typeKeywords`. These may be substantially different from the default values assigned during the item's creation. This can provide a number of unintended consequences, most notably with the Site Application item type where the lack of a `hubsubdomain|some-site` keyword effectively removes access to the site.

**To Reproduce**
Steps to reproduce the behavior:
```python
# we assume here a variety of item types: Dashboard, Web Experience, Feature Service, Web Map, Site Application
source = arcgis.gis.GIS()
for item in itemid_list:
source_item = source.content.get(item)
print(f"{source_item.itemid} | {source_item.type} | {source_item.title} | {source_item.owner}")
print(f"\ttypeKeywords: {source_item.typeKeywords}")
print("\tupdating typeKeywords with 'TEST-keyword'")
source_item.update({"typeKeywords": "TEST-keyword"})
source_item = source.content.get(item)
print(f"\ttypeKeywords: {source_item.typeKeywords}\n")
```
error:
```
c5b57fbdaeeb4973a8560c25119ec118 | Dashboard | bug - dashboard | some_user
typeKeywords: ['ArcGIS Dashboards', 'Dashboard', 'Operations Dashboard']
updating typeKeywords with 'TEST-keyword'
typeKeywords: ['Dashboard', 'Operations Dashboard', 'TEST-keyword']

c709fad59c504db09823bb86f11ac4ae | Web Experience | bug - exb | some_user
typeKeywords: ['EXB Experience', 'JavaScript', 'Ready To Use', 'status: Published', 'version:1.10.0', 'Web Application', 'Web Experience', 'Web Mapping Application', 'Web Page', 'Web Site']
updating typeKeywords with 'TEST-keyword'
typeKeywords: ['TEST-keyword', 'Web Application', 'Web Experience', 'Web Mapping Application', 'Web Page', 'Web Site']

70c702e1ed34496c938738a387b70aae | Feature Service | bug - feature layers | some_user
typeKeywords: ['ArcGIS Server', 'Data', 'Feature Access', 'Feature Service', 'providerSDS', 'Service', 'Hosted Service']
updating typeKeywords with 'TEST-keyword'
typeKeywords: ['ArcGIS Server', 'Data', 'Feature Access', 'Feature Service', 'Service', 'TEST-keyword', 'Hosted Service']

3c7862694aed46bd9aa0a30947ddf532 | Web Map | bug - web map | some_user
typeKeywords: ['ArcGIS API for JavaScript', 'ArcGIS Online', 'Collector', 'Data Editing', 'Explorer Web Map', 'Map', 'Online Map', 'Web Map']
updating typeKeywords with 'TEST-keyword'
typeKeywords: ['ArcGIS Online', 'Explorer Web Map', 'Map', 'Online Map', 'TEST-keyword', 'Web Map']

744dd182177f4c5f8f62f929c9d1b457 | Site Application | bug - site | some_user
typeKeywords: ['Hub', 'hubSite', 'hubSolution', 'hubsubdomain|bug-site', 'JavaScript', 'Map', 'Mapping Site', 'Online Map', 'OpenData', 'Ready To Use', 'selfConfigured', 'source-embedded-portal-default-site', 'state:hasUnpublishedChanges', 'Web Map']
updating typeKeywords with 'TEST-keyword'
typeKeywords: ['Hub', 'OpenData', 'TEST-keyword']
```

**Expected behavior**
The current documentation is lackluster for those unfamiliar with using the ArcGIS REST API, when utilizing `update` my expectation is that it appends a singular value, and wholesale replacement of the values would require a comma separated list. This erroneous thought process was compounded by the fact that items continued to operate, returned a number of `typeKeywords` including the singular value that was provided. As stated above, this behavior was not fully understood until the Site Application became inoperative.

A few thoughts,
- first, this section in the documentation could be expanded to make this behavior more explicit / clear.
-- [developers.arcgis.com/python/api-reference/arcgis.gis.toc.html#arcgis.gis.Item.update](https://developers.arcgis.com/python/api-reference/arcgis.gis.toc.html#arcgis.gis.Item.update)
-- a discussion on how `update` will remove all current parameters for a given key-value pair
-- notes on default parameters being created (to try and prevent an item from becoming inoperative)
-- example usage for the ingestion of list-based values
- second, `append`/`remove` parameters could be added to the update function to allow more fine-grained control on the simple addition/removal of values.
-- This would be a quality of life improvement to allow more pythonic operation instead of full replacement for what could be a single item addition/removal
-- The current methodology for adding a value is a bit circuitous:
```py
list_typeKeywords = item.typeKeywords
list_typeKeywords.append("some new keyword")
text_typeKeywords = ",".join(list_typeKeywords)
item.update({"typeKeywords": text_typeKeywords})
```
- third, if the API is going to attempt to provide defaults, those ideally would match the `typeKeywords` generated at item creation

**Platform (please complete the following information):**
- OS: Windows 11
- VS Code
- Python API Version `2.3.0.2`]