Clarify behaviour of http.proxySupport and http.useLocalProxyConfiguration settings

[kurtismash]

• Updates the description of the http.proxySupport and http.useLocalProxyConfiguration settings to clarify their behaviour. With the original wording I had understood it to mean that the remote host would use its local configuration when true.
• Adds missing "and" to the description of multiple proxy settings.

[Copilot]

Pull request overview

This PR improves the clarity and grammar of HTTP proxy-related configuration setting descriptions. The original wording was ambiguous about which host's proxy configuration was being referenced in remote development scenarios.

Key changes:

• Clarified that http.useLocalProxyConfiguration controls whether the VS Code host's local proxy settings are used by the remote extension host
• Fixed missing "and" conjunction in six proxy setting descriptions that describe behavior during remote development
• Changed "proxy support" to "proxy configuration" in the http.proxySupport description for better terminology consistency