feat: run transaction hooks at boundaries and add configurable LTO flags

- execute transaction pre hooks at transaction start and post hooks at transaction end
- add batched hook execution with ordered "(n/total)" logging
- refactor install flows to plan package actions first, then run hooks around commits
- add `build.flags.ltoflags` and `build.flags.use_lto` (default: true)
- export `LTOFLAGS` and append LTO flags to `CFLAGS`, `CXXFLAGS`, and `LDFLAGS`
  unless `use_lto = false`
- make autotools CFLAGS expansion use the final computed CFLAGS value
- update spec parsing/appends, interactive TOML output, docs, and contrib build config
- bump project version to 0.8.0 and update `zip` to 8.2.0

Cargo.lock

@@ -382,7 +382,7 @@ checksum = "807800ff3288b621186fe0a8f3392c4652068257302709c24efd918c3dffcdc2"
 
 [[package]]
 name = "depot"
-version = "0.7.0"
+version = "0.8.0"
 dependencies = [
  "anyhow",
  "ar",
@@ -2995,9 +2995,9 @@ dependencies = [
 
 [[package]]
 name = "zip"
-version = "8.1.0"
+version = "8.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6e499faf5c6b97a0d086f4a8733de6d47aee2252b8127962439d8d4311a73f72"
+checksum = "b680f2a0cd479b4cff6e1233c483fdead418106eae419dc60200ae9850f6d004"
 dependencies = [
  "aes",
  "bzip2",