Possible improvements to entropy-tss test environment

[ameba23]

This issue bundles together 3 possible improvements to the entropy-tss testing setup following #1147 which could be done as follow ups:

• Use a struct as a return value from the spawn_tss_nodes_and_start_chain function - as it currently returns a tuple with 5 fields - suggested by @HCastano : Allow offchain worker requests to all TSS nodes in entropy-tss test environment  #1147 (comment)
• Consider using feature flags to allow enabling the entropy-tss unsafe API when calling spawn_tss_nodes_and_start_chain from entropy-testing-utils, as @dvdplm suggested: https://github.com/entropyxyz/entropy-core/pull/1147/files/18c91cc6e3fa81888bc08eefb1676c6a956afa27#r1864869983
• Consider putting back the development chainspec as a variant of ChainSpecType to allow testing using the development chainspec. I removed it because we currently don't use it. See comment: Allow offchain worker requests to all TSS nodes in entropy-tss test environment  #1147 (comment)