fix: pass context to provider for stream data parsing

[brookhong]

Fix bedrock error on parsing

Error executing vim.schedule lua callback: ...re/nvim/lazy/avante.nvim/lua/avante/providers/claude.lua:177: attempt to index local 'content_block' (a nil value)
stack traceback:
    ...re/nvim/lazy/avante.nvim/lua/avante/providers/claude.lua:177: in function 'parse_response'
    ...e/nvim/lazy/avante.nvim/lua/avante/providers/bedrock.lua:40: in function 'parse_stream_data'
    ...ng/.local/share/nvim/lazy/avante.nvim/lua/avante/llm.lua:291: in function <...ng/.local/share/nvim/lazy/avante.nvim/lua/avante/llm.lua:280>
Error executing vim.schedule lua callback: ...re/nvim/lazy/avante.nvim/lua/avante/providers/claude.lua:177: attempt to index local 'content_block' (a nil value)
stack traceback:
    ...re/nvim/lazy/avante.nvim/lua/avante/providers/claude.lua:177: in function 'parse_response'
    ...e/nvim/lazy/avante.nvim/lua/avante/providers/bedrock.lua:40: in function 'parse_stream_data'
    ...ng/.local/share/nvim/lazy/avante.nvim/lua/avante/llm.lua:291: in function <...ng/.local/share/nvim/lazy/avante.nvim/lua/avante/llm.lua:280>

We need pass response context to the provider to parse stream data.