Reduce allocations from parsing include params

[ashmaroli]

Problem

Tags::IncludeTag#parse_params is called from within the :render method. to generate the Hash object for context["include"] from string markup by using a regex. Consequently, if an include is rendered numerous times, a lot of intermediate objects get allocated.

Prior art

The allocations were partially reduced for v4.2.0 in #8192.

Current Proposal

• Move parsing markup via regex into the :initialize method. The final Hash is however generated only via :render calls.
• Add new IncludeTag::ParameterTokenList class to avoid generating new Hashes if the params are context-agnostic (i.e. no variable).

Additional Notes

Also includes a benchmark script that compares current proposal with v4.2 optimization and pre-v4.2 implementation.