x/tools/gopls: support "inline all" and "inline away"

[findleyr]

Add two new code actions for inlining, defined at the callee rather than caller:

• "inline all" inlines all uses of a function
• "inline away" inlines all uses, and additionally removes the function declaration

[adonovan]

See also:

• x/tools/gopls: add refactor.inline.variable-all code action #70085 (extract is done)
• x/tools/internal/refactor/inline: offer an option to inline all calls in a file #68567 (inline all calls within a single file)