Fix interactive R and Python plots on Server Web and Workbench

[sharon-wang]

Description

• part of URL reshaping and proxying for Positron localhost URLs on Posit Workbench #4274
• addresses Positron Web: Various R plot packages don't work (similar issue between packages) #4804
• should unblock Fix resizing plotly web clients #4806, where the new plotly rendering method relies on a proxy server instead of an HTML file proxy

Changes

• add a new command to create a generic proxy server positronProxy.startHttpProxyServer
• rename the command positronProxy.stopHelpProxyServer to positronProxy.stopProxyServer since it is not help-specific
• rename resources/scripts.html to resources/scripts_help.html since it is help-specific
• move the src/href rewriting to a private reusable function rewriteUrlsWithProxyPath, which is now used by the generic http proxy and the help proxy contentRewriter
• update src/vs/code/browser/workbench/workbench.ts to resolve the uri while maintaining the uri's original path, query string and fragment strings (NOTE: needs to be contributed upstream)
• update src/vs/workbench/services/languageRuntime/common/languageRuntimeUiClient.ts to choose between starting an HTML file proxy if a file is being served or a generic http proxy if the content is not a file

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!