Ran a sed rule to replace most instances of //bt to //bt/system in all
BUILD.gn and *.gni files. Also made some manual changes to include
directories using packetgen and dumpsys to include bt/system/gd instead
of just bt/gd. Added a new BUILD.gn at root that just points to
system/BUILD.gn.

On the Rust side, updated the Cargo.toml paths and build.rs includes for
topshim.

Bug: 205591223
Test: Run `./build.py`
Tag: #floss
Change-Id: Ib6b9b991f140742d765a1031c8f4085aba9ce552

This reverts commit ddd429fe.

As it turns out, we will need to change //bt to //bt/system after all
because the ChromeOS ebuild can't easily handle the subdirectory change
otherwise.

Bug: 205591223
Test: Run `./build.py`
Tag: #floss
Change-Id: I620221cb589712dfc1f84c7ea87a175634a86250

Bug: 188074901
Tag: #refactor
Test: gd/cert/run

Change-Id: Ifc7d6e2eee27e4d15acf34318c8d3b883d85d72d

Bug: 188074901
Tag: #refactor
Test: gd/cert/run

Change-Id: Id1301da0a146cb71fcbc7970af8887ab9bce860d

Tag: #refactor
Bug: 197044261
Test: manual
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 lines

Change-Id: Icbe1e00099ef85cbd21e82f4da0c82ec287afbfb
Merged-In: Icbe1e00099ef85cbd21e82f4da0c82ec287afbfb

Test: cert/run
Bug: 197316386
Tag: #feature
Change-Id: I74f203d756350905f146a36ce1d7b3015688cf8f

Bug: 191555414
Tag: #refactor
Test: gd/cert/run

Change-Id: I36ed463face105b824ef3854b742734b3329af7a

Bug: 202068782
Tag: #refactor
Test: gd/cert/run

Change-Id: I00564abbb638a45316b53609504bc35abbb63355

Bug: 187830698
Tag: #refactor
Test: gd/cert/run

Change-Id: Iaa604d15509b0881efb2e779ebab1d481278a91c

Bug: 199945370
Tag: #refactor
Test: gd/cert/run

Change-Id: I33ec0248e0e8baaf79fae32b7a9ee1e6a28ecc7b

Cargo was not rerunning build.rs for linking when there were new C++
libraries available. This adds a rerun-if that checks the C++ output
directory for changes when making this decision.

Bug: 203696027
Tag: #floss
Test: ./build.py with C++ changes only and confirm changes applied
Change-Id: I46c968ce92ffddb7538b31df2103b79b0377fe3a

Bug: 195157393
Tag: #floss
Test: Build floss on linux

Change-Id: Iccc984f7f682840e03a1073aecdb27f6e2ad5c94

The `len` parameter is not useful in the Rust/D-Bus interface since an
the length is already provided in an array data type.

Bug: 202334519
Tag: #floss
Test: Build floss on Linux

Change-Id: I3acd58b996f0f158913e1f5f0ce20b652b6b26d3

Bug: 203417776
Tag: #refactor
Test: gd/cert/run
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 lines

Change-Id: I80ba9895148918d159974cce0efe4ce97683b8d6

Bug: 188074901
Tag: #refactor
Test: gd/cert/run

Change-Id: I227dbe4f280d088c5870b92fbb117b1a3cc61a0d

Bug: 188074901
Tag: #refactor
Test: gd/cert/run
Change-Id: If51f5603ad47c862d34d2eb0483b5328ee486e6e

Bug: 187824969
Tag: #refactor
Test: gd/cert/run
Change-Id: Ie4afcb6a07e28fe3454f310ac8f340e0a9b701ff

Bug: 187824969
Tag: #refactor
Test: gd/cert/run

Change-Id: I0c74c582bd1d50af1890e4b5a3228e0183eaef2c

Bug: 188074901
Tag: #refactor
Test: gd/cert/run

Change-Id: I8486ffb98519f1f2d56191f964d87df27909fffd

Bug: 188074901
Tag: #refactor
Test: gd/cert/run

Change-Id: I908e83dc8155142db2fef3dc961883789529f681

Bug: 188074901
Tag: #refactor
Test: gd/cert/run
Change-Id: I21b5c711781f5909b17263d5ce2b7f19bfef19d9

Bug: 188074901
Tag: #refactor
Test: gd/cert/run

Change-Id: Iea1b64d0daf176100b4ca47362b67357f901662a

Bug: 202018502
Test: cert/run
Tag: #feature
Change-Id: I9e9ca3c27f41921777d940946475dfc5f79ab4ac

Bug: 203417776
Tag: #refactor
Test: gd/cert/run
Change-Id: I81a48f1d2bb3d8b59eaa0640855d077fc095db1a