always send html plot content to a proxy server

[sharon-wang]

Description

A follow-up to #4806 to revert src/vs/workbench/services/languageRuntime/common/languageRuntimeUiClient.ts back to using a proxy for interactive plots. A generic HTTP proxy was added via #4855, so server plots can be proxied appropriately in Server Web and Workbench.

Related to

• Positron Web: Various R plot packages don't work (similar issue between packages) #4804
• URL reshaping and proxying for Positron localhost URLs on Posit Workbench #4274
• Interactive plots do not fill the plot area until redrawn by switching focus #4245

QA Notes

On Server Web and Workbench, running the following in the corresponding consoles:

Python

pip install plotly nbformat pandas

import plotly.express as px
fig = px.bar(x=["a", "b", "c"], y=[1, 3, 2])
fig.show()

R

install.packages('plotly')

library(plotly)
fig <- plot_ly(data = iris, x = ~Sepal.Length, y = ~Petal.Length)
fig

Expected Result

The corresponding interactive plots should display in the plots pane and be interact-able!

[timtmok]

👍