Monomorphize various things (#1914)
Based on #1910
This shrinks breakout from 310k to 293k. Most of the win is in outlining the drop glue of `App`. The other two commits save about 800 bytes total when using two empty systems and two simple resources.
After this PR the full disassembly for
```rust
fn main() {
App::build().run();
}
```
is about as minimal as it gets, so pretty much all other costs scale linear in the amount of resources, systems, etc.
```asm
0000000000001100 <_ZN4core3ptr54drop_in_place$LT$bevy_app..app_builder..AppBuilder$GT$17h76850422c20653deE>:
1100: ff 25 52 21 00 00 jmpq *0x2152(%rip) # 3258 <_ZN60_$LT$bevy_app..app..App$u20$as$u20$core..ops..drop..Drop$GT$4drop17h67d177ae549d917bE@Base>
1106: cc int3
1107: cc int3
1108: cc int3
1109: cc int3
110a: cc int3
110b: cc int3
110c: cc int3
110d: cc int3
110e: cc int3
110f: cc int3
0000000000001110 <_ZN8breakout4main17h7cbe07b319de1042E>:
1110: 53 push %rbx
1111: 48 81 ec 00 03 00 00 sub $0x300,%rsp
1118: 48 8d 5c 24 08 lea 0x8(%rsp),%rbx
111d: 48 89 df mov %rbx,%rdi
1120: ff 15 3a 21 00 00 callq *0x213a(%rip) # 3260 <_ZN8bevy_app3app3App5build17h8b0ea6be9050d6ccE@Base>
1126: 48 89 df mov %rbx,%rdi
1129: ff 15 39 21 00 00 callq *0x2139(%rip) # 3268 <_ZN8bevy_app11app_builder10AppBuilder3run17hfc8cf50692acdbdeE@Base>
112f: 48 8d 7c 24 08 lea 0x8(%rsp),%rdi
1134: ff 15 1e 21 00 00 callq *0x211e(%rip) # 3258 <_ZN60_$LT$bevy_app..app..App$u20$as$u20$core..ops..drop..Drop$GT$4drop17h67d177ae549d917bE@Base>
113a: 48 81 c4 00 03 00 00 add $0x300,%rsp
1141: 5b pop %rbx
1142: c3 retq
1143: 48 89 c3 mov %rax,%rbx
1146: 48 8d 7c 24 08 lea 0x8(%rsp),%rdi
114b: e8 b0 ff ff ff callq 1100 <_ZN4core3ptr54drop_in_place$LT$bevy_app..app_builder..AppBuilder$GT$17h76850422c20653deE>
1150: 48 89 df mov %rbx,%rdi
1153: e8 18 01 00 00 callq 1270 <_Unwind_Resume@plt>
1158: 0f 0b ud2
115a: cc int3
115b: cc int3
115c: cc int3
115d: cc int3
115e: cc int3
115f: cc int3
0000000000001160 <main>:
1160: 48 83 ec 08 sub $0x8,%rsp
1164: 48 89 f1 mov %rsi,%rcx
1167: 48 63 d7 movslq %edi,%rdx
116a: 48 8d 05 9f ff ff ff lea -0x61(%rip),%rax # 1110 <_ZN8breakout4main17h7cbe07b319de1042E>
1171: 48 89 04 24 mov %rax,(%rsp)
1175: 48 8d 35 94 1e 00 00 lea 0x1e94(%rip),%rsi # 3010 <__init_array_end>
117c: 48 89 e7 mov %rsp,%rdi
117f: ff 15 eb 20 00 00 callq *0x20eb(%rip) # 3270 <_ZN3std2rt19lang_start_internal17he77194431b0ee4a2E@Base>
1185: 59 pop %rcx
1186: c3 retq
1187: cc int3
1188: cc int3
1189: cc int3
118a: cc int3
118b: cc int3
118c: cc int3
118d: cc int3
118e: cc int3
118f: cc int3
0000000000001190 <_ZN3std2rt10lang_start28_$u7b$$u7b$closure$u7d$$u7d$17h83a5b8d55f23dff8E.llvm.909376793398482062>:
1190: 48 83 ec 08 sub $0x8,%rsp
1194: 48 8b 3f mov (%rdi),%rdi
1197: e8 54 ff ff ff callq 10f0 <_ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17h6e238af75680eb28E>
119c: 31 c0 xor %eax,%eax
119e: 59 pop %rcx
119f: c3 retq
00000000000011a0 <_ZN4core3ops8function6FnOnce40call_once$u7b$$u7b$vtable.shim$u7d$$u7d$17hb05d591cd29dea4fE.llvm.909376793398482062>:
11a0: 48 83 ec 08 sub $0x8,%rsp
11a4: 48 8b 3f mov (%rdi),%rdi
11a7: e8 44 ff ff ff callq 10f0 <_ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17h6e238af75680eb28E>
11ac: 31 c0 xor %eax,%eax
11ae: 59 pop %rcx
11af: c3 retq
00000000000011b0 <_ZN4core3ptr85drop_in_place$LT$std..rt..lang_start$LT$$LP$$RP$$GT$..$u7b$$u7b$closure$u7d$$u7d$$GT$17he9aeeba375093b99E.llvm.909376793398482062>:
11b0: c3 retq
11b1: cc int3
11b2: cc int3
11b3: cc int3
11b4: cc int3
11b5: cc int3
11b6: cc int3
11b7: cc int3
11b8: cc int3
11b9: cc int3
11ba: cc int3
11bb: cc int3
11bc: cc int3
11bd: cc int3
11be: cc int3
11bf: cc int3
```
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