esp32: Provision to redirect .bss to external ram through linker fragments

Include external ram section in the linker template to process it
through linker script generation mechanism. This enables redirection of .bss section to external memory using linker fragments

libnet80211, libpp, libbt, liblwip: Redirect .bss through fragments

components/esp32/ld/esp32_fragments.lf

@@ -15,6 +15,18 @@ entries:
 entries:
     COMMON
 
+[sections:legacy_bss]
+entries:
+    .dynsbss
+    .sbss+
+    .gnu.linkonce.sb+
+    .scommon
+    .sbss2+
+    .gnu.linkonce.sb2+
+    .dynbss
+    .share.mem
+    .gnu.linkonce.b+
+
 [sections:rodata]
 entries:
     .rodata+
@@ -64,6 +76,10 @@ entries:
 entries:
     .iram.bss+
 
+[sections:extram_bss]
+entries:
+    .ext_ram.bss+
+
 [sections:dram]
 entries:
     .dram1+
@@ -87,6 +103,11 @@ entries:
     data -> dram0_data
     bss -> dram0_bss
     common -> dram0_bss
+    if SPIRAM_ALLOW_BSS_SEG_EXTERNAL_MEMORY = y:
+        extram_bss -> extern_ram
+    else:
+        extram_bss -> dram0_bss
+    legacy_bss -> dram0_bss
     iram -> iram0_text
     iram_data -> iram0_data
     iram_bss -> iram0_bss
@@ -130,3 +151,8 @@ entries:
 [scheme:wifi_rx_iram]
 entries:
     wifi_rx_iram -> iram0_text
+
+[scheme:extram_bss]
+entries:
+    bss -> extern_ram
+    common -> extern_ram