[Proposal] Remove `reverse_tpk_map` and `reverse_tcm_map`

[howardwu]

💥 Proposal

Currently, neither of these maps are being used:

/// Returns the reverse `tpk` map.
fn reverse_tpk_map(&self) -> &Self::ReverseTPKMap;

/// Returns the reverse `tcm` map.
fn reverse_tcm_map(&self) -> &Self::ReverseTCMMap;

If there are developers who value these, please chime in here.